Fermentation, Volume 9, Issue 8 (August 2023) – 82 articles

This review paper provides an overview of various types of photobioreactors (PBRs) that could be used for the production of polyhydroxyalkanoates (PHAs) using anoxygenic photoheterotrophs, with a focus on the design and operation of these systems. The paper highlights the potential of different PBRs based on reactor geometry and growth mode, and also examines the advantages and disadvantages of each PBR type and summarizes their suitability for PNSB-PHA production. The optimization of reactor design and operation is crucial for maximizing PNSB growth and PHA productivity. The self-immobilization of bacteria in granular sludge is a promising technology for wastewater treatment and the production of PHAs, while grooved-surface PBRs and porous-substrate PBRs have limitations due to difficult biomass harvesting in the former and the presence of aerobic conditions incongruent with PNSB culturing in the latter. Limitations exist with all solutions for maximizing rapid growth and maintaining high biomass concentrations due to the requirements of phototrophic growth. Full article

(1) Background: Previous studies have indicated that ferulic acid esterase (FAE), cellulase and xylanase have synergistic effects in lignocellulose degradation, and the cutting stage has a major impact on silages. Whether these additives affect the silages at different cutting stages is unclear. (2) Methods: Sudangrass height at the tested cutting stages was 1.8 m (S1) and 2.0 m (S2). The silage from the two cutting stages was treated with FAE-producing Lactobacillus plantarum (LP), cellulase and xylanase (CX) and a combination of LP and CX (LP+CX) for 30 and 60 days. (3) Results: Compared with CK, adding LP+CX significantly decreased the pH and the content of neutral detergent fiber (NDF) and acidic detergent fiber (ADF) (p < 0.05) and increased the lactic acid (LA) concentration (p < 0.05), dry matter (DM) content and crude protein content. Adding LP+CX effectively degraded lignocellulose in sudangrass, and the NDF and ADF degradation rates at the two stages were all more than 30%. In comparison, cutting at the S2 stage led to a lower pH and higher LA and DM contents (p < 0.05). Additives and the cutting stage exerted a strong effect on the silage microbial community, and Firmicutes and Lactiplantibacillus became the most dominant bacterial phyla and genera, especially at the S2 stage. (4) Conclusions: The results suggest that FAE-producing L. plantarum, cellulase and xylanase had synergistic effects on sudangrass silages, especially at the S2 stage, and their use can thus serve as an efficient method for ensiling. Full article

Polyaluminum chloride (PAC) is used widely and increasingly in wastewater treatment plants, resulting in its inevitably high production in sludge. Previous studies have indicated that the production of short-chain fatty acids (SCFAs) is inhibited by the existence of PAC in sludge anaerobic fermentation, so it is necessary to study how to promote sludge anaerobic fermentation under low concentrations of PAC. In this study, sodium citrate (SC) was first used to improve the efficiency of anaerobic fermentation under low concentrations of PAC. The results showed that the production of SCFAs increased with SC, especially when the ratio of PAC to SC was 1:2, and the maximum production of SCFAs reached 2890 mg/L, which is 2.5 times more than when PAC only exists. The mechanism studies showed that SC could remove the Al³⁺ in the sludge floc, which led to deflocculation of the sludge floc, accelerated the destruction of extracellular polymers (EPS), and released soluble substances in the sludge. At the same time, the key enzymes that were bound and hidden originally in the sludge were also released, which promoted the further degradation of organic matter and shortened the anaerobic fermentation period. However, the higher concentration of SC was not conducive to sludge dehydration. Therefore, the optimal distribution ratio of PAC to SC should be 1:1. This study provides a new idea for the research and practical application of sludge anaerobic fermentation. Full article

The efficient conversion of cellulosic sugars is vital for the economically viable production of biofuels/biochemicals from lignocellulosic biomass hydrolysates. Based on comprehensive screening, Saccharomyces cerevisiae RC212 was chosen as the chassis strain for multiple integrations of heterologous β-glucosidase and β-xylosidase genes in the present study. The resulting recombinant BLN26 and LF1 form a binary synthetic consortium, and this co-culture system achieved partial fermentation of four sugars (glucose, xylose, cellobiose, and xylo-oligosaccharides). Then, we developed a ternary S. cerevisiae consortium consisting of LF1, BSGIBX, and 102SB. Almost all four sugars were efficiently fermented to ethanol within 24 h, and the ethanol yield is 0.482 g g⁻¹ based on the consumed sugar. To our knowledge, this study represents the first exploration of the conversion of mixtures of glucose, xylose, cellobiose, and xylo-oligosaccharides by a synthetic consortium of recombinant S. cerevisiae strains. This synthetic consortium and subsequent improved ones have the potential to be used as microbial platforms to produce a wide array of biochemicals from lignocellulosic hydrolysates. Full article

The increasing share of renewable electricity in the grid drives the need for sufficient storage capacity. Especially for seasonal storage, power-to-gas can be a promising approach. Biologically produced methane from hydrogen produced from surplus electricity can be used to substitute natural gas in the existing infrastructure. Current reactor types are not or are poorly optimized for flexible methanation. Therefore, this work proposes a new reactor type with a plug flow reactor (PFR) design. Simulations in COMSOL Multiphysics ^® showed promising properties for operation in laminar flow. An experiment was conducted to support the simulation results and to determine the gas fraction of the novel reactor, which was measured to be 29%. Based on these simulations and experimental results, the reactor was constructed as a 14 m long, 50 mm diameter tube with a meandering orientation. Data processing was established, and a step experiment was performed. In addition, a k_La of 1 h⁻¹ was determined. The results revealed that the experimental outcomes of the type of flow and gas fractions are in line with the theoretical simulation. The new design shows promising properties for flexible methanation and will be tested. Full article

Yeast assimilable nitrogen (YAN), besides the oenological parameters (sugar content, titratable acidity, and pH) in grape musts of sixteen native and international varieties of Vitis vinifera cultivated in six regions of Northern Greece, was assessed in the frame of the present study. Low levels of YAN are frequently thought to be the cause of problematic fermentations and originate significant changes in the organoleptic aspects of the finished product. The objective of this multi-variety study was to assess factors affecting the YAN amount and composition in technologically mature grapes and, therefore, to evaluate the necessity of YAN supplementation with ammonium salts in musts across different native and international grape varieties. Free amino nitrogen was measured colorimetrically, ammoniacal nitrogen was measured enzymatically, and their values for each must sample were summed to obtain the total amount of YAN. Statistical analysis was carried out including principal component analysis (PCA) to discover relationships among must samples and the parameters studied. PCA analysis classified samples depending on grape varieties and region of origin, bringing knowledge about native and international cultivars of great commercial interest. Moreover, these findings could help to understand how commercial varieties can behave in different climates in the climate change context. Full article

Traditional Chinese strong-aroma baijiu (CSAB) fermentation technology has been used for thousands of years. Microbial communities that are enriched in continuous and uninterrupted fermentation pits (FPs) are important for fermentation. However, changes in the metabolic functional genes in microbial communities of FPs are still under-characterized. High-throughput sequencing technology was applied to comprehensively analyze the diversity, function, and dynamics of the metabolic genes among FPs of different ages, positions, and geographical regions. Approximately 1,375,660 microbial genes derived from 259 Gb metagenomic sequences of FPs were assembled and characterized to understand the impact of FP microorganisms on the quality of CSAB and to assess their genetic potential. The core functional gene catalog of FPs, consisting of 3379 ubiquitously known gene clusters, was established using Venn analysis. The functional profile confirmed that the flavor compounds in CSAB mainly originate from the metabolism of carbohydrates and amino acids. Approximately 17 key gene clusters that determine the yield and quality of CSAB were identified. The potential mechanism was associated with the biosynthesis of host compounds in CSAB, which relies on the abundance of species, such as Lactobacillus, Clostridium, Saccharomycetales, and the abundance of functional genes, such as CoA dehydrogenase, CoA transferase, and NAD dehydrogenase. Furthermore, the detailed metabolic pathways for the production of main flavor compounds of CSAB were revealed. This study provides a theoretical reference for a deeper understanding of substance metabolism during CSAB brewing and may help guide the future exploration of novel gene resources for biotechnological applications. Full article

Third-generation (3G) biorefineries harnessing industrial off-gases have received significant attention in the transition towards a sustainable circular economy. However, uncertainties surrounding their techno-economic feasibility are hampering widespread commercialization to date. This study investigates the production of single-cell protein (SCP), a sustainable alternative food and feed protein, from steel mill off-gas through an efficient coupled fermentation approach utilizing acetate as an intermediate. A comprehensive model that comprises both the gas-to-acetate and the acetate-to-SCP fermentation processes, as well as gas pretreatment and downstream processing (DSP) operations, was developed and used to perform a techno-economic analysis (TEA). Sensitivity analyses demonstrated that significant cost reductions can be achieved by the process intensification of the gas-to-acetate fermentation. As such, an increase in the acetate concentration to 45 g/L and productivity to 4 g/L/h could lead to a potential cost reduction from 4.15 to 2.78 USD/kg. In addition, the influence of the production scale and other economic considerations towards the commercialization of off-gas-based SCPs are discussed. Conclusively, this research sheds light on the practical viability of a coupled fermentation process for SCP production by identifying key cost-influencing factors and providing targets for further optimization of the acetate platform, fostering sustainable and economically feasible bio-based innovations. Full article

Polyphenol oxidase and its isoenzymes are crucial enzymes in the tea tree that catalyze the synthesis of theaflavins. In this study, tea tree polyphenol oxidase was used as the research object, and various protein sequence treatments, such as TrxA fusion tag + N-terminal truncation, were tested for prokaryotic expression through the Escherichia coli expression system. Comparative analyses were conducted on the activities of the different recombinant enzyme proteins on the substrates of tea polyphenol fractions. Additionally, the enzyme with the highest catalytic efficiency on the TFDG substrate was immobilized using polyethylene glycol to investigate the yield of its synthesis of TFDG. Our results demonstrated that after N-terminal truncation and TrxA fusion expression, CsPPO1, CsPPO2, CsPPO3, and CsPPO4 were mostly expressed in the form of inclusion bodies in the cell and exhibited varying degrees of enhancement in substrate activity. Specifically, CsPPO1 exhibited significantly increased activity in EC and ECG, CsPPO2 showed enhanced activity towards ECG and EGCG, and CsPPO2 displayed the highest activity toward TFDG substrates. Homology modeling structural analysis of the polyphenol oxidase isozymes revealed that the active centers of CsPPO1, CsPPO2, and CsPPO3 consisted of double copper ion center structures, while the conserved histidine residues surrounding the active centers formed different catalytic activity centers in different structures. Furthermore, polyethylene glycol immobilization significantly increased the activity recovery of the CsPPO2 enzyme to 74.41%. In summary, our study elucidated that tea tree polyphenol oxidase is expressed as inclusion bodies in prokaryotic expression, and the activity of the recombinant enzyme towards substrates could be enhanced through N-terminal truncation and TrxA fusion expression. Moreover, immobilization treatment of the CsPPO2 enzyme greatly improved enzyme efficiency. These findings offer an important enzymatic basis and theoretical support for the synthesis of theaflavins. Full article

This study evaluates the potential to synthesize an adsorbent for wastewater remediation applications from an anaerobic digestion by-product synthesized using biomaterials and a less energy-intensive process. The synthesized sludge-based granular activated carbon (GAC) was used to adsorb Cr(VI) and Cd(II) in a batch reactor stirred for 24 h at 25 °C. The surface chemistry of the material was assessed porosity with BET, SEM for morphology, EDS-XRF for elemental analysis, and functional groups on these materials using FTIR and TGA for thermal profile. S_BET of the SAC was discovered to be 481.370 m²/g with a V_T of 0.337 cm³/g, respectively 9.02 and 2.23 times greater than raw sludge. The modification to SAC shows a dramatic increase in performance from 40% to 98.9% equilibrium adsorption rate. The maximum or equilibrium removal (99.99%) of Cr(VI) and Cd(II) was achieved by 0.8 and 1.4 g SAC dosage, respectively. Thus, it can be concluded that activation of sewage sludge was effective in enhancing the surface area and pore volume which made it suitable for AMD remediation application. Full article

Microalgae are recognized as a promising and valuable source of lutein. However, the current two-stage method for lutein production has drawbacks, such as complex operations and a long cultivation time. Additionally, utilizing heterotrophic fermentation to cultivate microalgae for lutein production leads to low lutein content due to the absence of light. In this study, we proposed a novel cultivation method that involves light induction of the seed culture to enhance lutein production during the heterotrophic cultivation phase of Chlorella protothecoides CS-41. To gain comprehensive insights into the underlying mechanisms of this method, we conducted qualitative and quantitative analyses of specific metabolites related to central carbon metabolism. The results revealed that low-light induction of seeds exhibited higher carbon efficiency compared to cells continuously subjected to heterotrophic cultivation, which may explain the observed increase in biomass and lutein content in cultures. Cultures after low-light induction of seed exhibited significantly higher lutein content (2.71 mg/g), yield (66.49 mg/L) and productivity (8.59 mg/L/d) compared to those consistently cultivated under heterotrophic conditions (2.37 mg/g, 37.45 mg/L, 4.68 mg/L/d). This cultivation strategy effectively enhances lutein yields, reduces production costs and holds the potential for broader application in other algal species for pigment production. Full article

Christensenella minuta (C. minuta), a member of a recently described bacterial family, is one of the most heritable next-generation probiotics. Many observational studies confirmed that the relative abundance of C. minuta is associated with lean body types with a low host body mass index (BMI), and is also influenced by age, diet, and genetics. By utilizing its benefits, it could be suited to many therapies, including human and animal health as well. However, a reliable method for culturing the strain must also be developed to enable the therapeutic administration of the microbe. Sludge microfiltration could be a promising solution for large scale-up cultivation. In this review, different processing methods are also described from pharmaceutical aspects. Full article

A randomized, double-blind, placebo-controlled trial was designed to assess the efficacy of the parabiotic Bifidobacterium breve IDCC 4401, named BBR 4401, for lowering cholesterol levels. The 66 subjects (per protocol set, n = 60) with low-density lipoprotein-cholesterol (LDL-C) levels between 100 mg/dL and 150 mg/dL were enrolled after a 4-week run-in period (e.g., no probiotics, low cholesterol diet and no food affecting lipid profiles). The two groups were prescribed 1 × 10¹⁰ (low-dose) and 1 × 10¹¹ CFU (high-dose), whereas the placebo group was prescribed 97% (w/w) of maltodextrin for 4 weeks. The compliance rates exceeded 97% in the subjects who completed the study. Comparison of the mean changes from baseline between the placebo group and test groups after the 12 weeks of BBR 4401 consumption showed a statistically significant reduction in LDL-C (up to −10.8%, p-value = 0.008) and apolipoproteinB (up to −8.1%, p-value = 0.008). Meanwhile, there were no clinically significant changes in vital signs, clinical pathology tests or electrocardiograms and no significant adverse events were reported during the study period. Concerning bowel habits, the consumption of BBR 4401 alleviated defecation strain, distension and watery feces in the high-dose group. Thus, BBR 4401 may be a safe and functional food for adults with moderate hypercholesterolemia. Full article

Lactic acid plays an important role in industrial applications ranging from the food industry to life sciences. The growing demand for lactic acid creates an urgent need to find economical and sustainable substrates for lactic acid production. Agricultural waste is rich in nutrients needed for microbial growth. Fermentative production of lactic acid from non-food-competing agricultural waste could reduce the cost of lactic acid production while addressing environmental concerns. This work provided an overview of lactic acid fermentation from different agricultural wastes. Although conventional fermentation approaches have been widely applied for decades, there are ongoing efforts toward enhanced lactic acid fermentation to meet the requirements of industrial productions and applications. In addition, agricultural waste contains a large proportion of pentose sugars. Most lactic-acid-producing microorganisms cannot utilize such reducing sugars. Therefore, advanced fermentation techniques are also discussed specifically for using agricultural waste feedstocks. This review provides valuable references and technical supports for the industrialization of lactic acid production from renewable materials. Full article

D-glucaric acid is an important bio-based building block of polymers and is a high value-added chemical that can be used in a variety of applications. In the present study, the Udh target genes from Pseudomonas putida and Pseudomonas syringae were used together to construct the expression vector pETDuet-2 × Udh. The transformants of BL21 (DE3) with vector pETDuet-2 × Udh were applied to produce glucaric acid from glucuronic acid. After optimizing the induction conditions, the highest Udh expression was achieved when 0.4 mmol·L⁻¹ isopropyl-β-d–thiogalactoside (IPTG) was added to the cell cultures at an OD₆₀₀ value of 0.6 followed by culturing at 26 °C for 6 h. The production of glucaric acid substantially reached 5.24 ± 0.015 g·L⁻¹ in fed-batch cultures in a 30 L tank. In the present study, a new system for glucaric acid production was established, which was more economic and friendly to the environment. Full article

Butyric acid (C4) and pyroglutamic acid (pGlu) exert significant beneficial effects on human health. In this study, the influence of probiotics (Lactobacillus acidophilus and Bifidobacteria) and/or prebiotics (1 and 3% inulin and fructo-oligosaccharides) on the content of C4 and pGlu in yoghurt during the shelf-life period was evaluated. The contents of C4 and pGlu were determined in probiotic, prebiotic and synbiotic yoghurts during 30 days of storage at 4 °C by solid-phase microextraction coupled with gas chromatography/mass spectrometry and HPLC analysis. Traditional yoghurt and uninoculated milk were used as control. Prebiotic yoghurt contained more C4 (2.2–2.4 mg/kg) than the uninoculated milk, and no increase was detected with respect to traditional yoghurt. However, probiotic yoghurt showed 10% more C4 than traditional yoghurt. Adding fibre to probiotics (synbiotic yoghurt) the C4 content increased by 30%. Regarding pGlu, probiotic yoghurt presented the highest content of approximately 130 mg/100 g. Fibre did not affect pGlu content. Finally, C4 and pGlu contents generally increased up to 20 days of storage and then decreased up to 30 days of storage. The results might be useful for the preparation of other functional foods rich in C4 and pGlu using lactic acid bacteria. Full article

Alzheimer’s disease (AD) is an ascending, neurodegenerative disorder that attacks the brain’s nerve cells, i.e., neurons, resulting in loss of memory, language skills, and thinking and behavioural changes. It is one of the most common causes of dementia, a group of disorders that is marked by the decline of cognitive functioning. Probiotics are living microorganisms that are beneficial for human well-being. They help in balancing the extent of bacteria in the gut and support the defensive immune system of the body. Studies have found that probiotics can help with a variety of conditions, including mental health. Probiotics are beneficial bacteria that can help to maintain and strengthen a healthy gut microbiome. The gut microbiome is important for healthy brain function, as it is linked to the production of neurotransmitters and hormones that regulate mood and behaviour. This review article includes detailed review on the origination of probiotics and its significance in the treatment of AD. Full article

Second-generation lactic acid production requires the development of sustainable and economically feasible processes and renewable lignocellulose biomass as a starting raw material. Weizmannia coagulans MA42 was isolated from a soil sample in Chiang Mai province, Thailand and showed the highest production of L-lactic acid and lignocellulolytic enzymes (cellulase, β-mannanase, xylanase, β-glucosidase, β-mannosidase, and β-xylosidase) compared to other isolates. Weizmannia coagulans MA42 was able to grow, secrete lignocellulolytic enzymes, and directly produce L-lactic acid in the medium containing various lignocellulosic feedstocks as the sole carbon source. Moreover, L-lactic acid production efficiency was improved after the substrates were pretreated with diluted sulfuric acid and diluted sodium hydroxide. The highest L-lactic acid production efficiency of 553.4 ± 2.9, 325.4 ± 4.1, 326.6 ± 4.4, 528.0 ± 7.2, and 547.0 ± 2.2 mg/g total available carbohydrate was obtained from respective pretreated substrates including sugarcane bagasse, sugarcane trash, corn stover, rice straw, and water hyacinth. It is suggested that structural complexity of the lignocellulosic materials and properties of lignocellulolytic enzymes are the key factors of consolidated bioprocessing (CBP) of lignocellulosic feedstocks to lactic acid. In addition, the results of this study indicated that W. coagulans MA42 is a potent bacterial candidate for CBP of a variety of lignocellulosic feedstocks to L-lactic acid production; however, further bioprocess development and genetic engineering technique would provide higher lactic acid production efficiency, and this would lead to sustainable lactic acid production from lignocellulosic feedstocks. Full article

In the present study, a total of eight Enterococcus faecium (OQ940301, OQ940302, OQ940303, OQ940304, OQ940305, OQ940308, OQ940309, and OQ940310) were isolated from soybean paste, a traditional Korean fermented food, and evaluated for their probiotic properties. The results showed that all the E. faecium strains survived in simulated human gastrointestinal conditions (4.1–5.59 log₁₀ CFU/mL). In addition, the range of auto-aggregation was 5–25%, the hydrophobicity was around 94%, and it exhibited significant co-aggregation ability with Salmonella enterica and Staphylococcus aureus. However, all the isolates were shown to be resistant to Gentamycin. The bacterial cell-free supernatant showed antibacterial activity against S. enterica, Escherichia coli, Bacillus cereus, Listeria monocytogenes, and S. aureus. Furthermore, E. faecium exhibited potent anti-oxidant activity by scavenging 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) free radicals. In addition, safety was confirmed by evaluating the hemolytic activity in blood agar; none of the bacterial isolates showed hemolysis. These results demonstrated that E. faecium (OQ940301 and OQ940309) isolated from soybean paste showed a higher probiotic potential. Full article

Evidence from the literature suggests that different inoculation strategies using either active dry yeast (ADY) or freshly prepared yeast cultures affect wine yeast performance, thus altering biomass and many primary and secondary metabolites produced during fermentation. Here, we investigated how different inoculation methods changed the fermentation behaviour and metabolism of a commercial wine yeast. Using a commercial Sauvignon blanc (SB) grape juice, fermentation was carried out with two different inoculum preparation protocols using Saccharomyces cerevisiae X5: rehydration of commercial ADY and preparation of pre-inoculum in a rich laboratory medium. We also determined the effect of different numbers of yeast cells inoculation (varying from 1 × 10⁶ to 1 × 10¹²) and successive inoculation on fermentation and end-product formation. The yeast inoculation method and number of cells significantly affected the fermentation time. Principal component analysis (PCA) using 60 wine metabolites showed a separation pattern between wines produced from the two inoculation methods. Inoculation methods influenced the production of amino acids and different aroma compounds, including ethyl and acetate esters. Varietal thiols, 3-mercaptohexanol (3MH), and 4-methyl-4-mercaptopentan-2-one (4MMP) in the wines were affected by the inoculation methods and numbers of inoculated cells, while little impact was observed on 3-mercaptohexyl acetate (3MHA) production. Pathway analysis using these quantified metabolites allowed us to identify the most significant pathways, most of which were related to central carbon metabolism, particularly metabolic pathways involving nitrogen and sulphur metabolism. Altogether, these results suggest that inoculation method and number of inoculated cells should be considered in the production of different wine styles. Full article

Ginkgo biloba seed (GBS) contains rich nutrients, such as starch, protein, oil, and trace components, such as flavonoids and terpene lactones. Due to its high protein content, it can be used as a raw material for fermentation and brewing. In this study, GBS was selected as the object of a fermentation process optimization test. Six kinds of fermentation starter were selected to brew ginkgo wine. The results showed that different fermentation starters have significant impacts on the composition of the wine. The yeast group had higher total sugar content and comprehensive evaluation scores than the Jiuqu group, while the total acid and total free amino acid contents showed the opposite result. The total flavonoid and total terpene lactone contents of the yeast group were 21.0% and 12.8% higher than those of the Jiuqu group, respectively. However, the 4′-O-methylpyridoxine (MPN) and 4′-O-methylpyridoxine-5′-glucoside (MPNG) contents of the yeast group were also 12.6% and 2.3% higher than those of the Jiuqu group, respectively. The common volatile components in the two groups of samples were isoamyl alcohol, phenethyl alcohol, ethyl octanoate, and phenethyl acetate. The antioxidant capacity of ginkgo wine fermented by yeast was significantly higher than that of the Jiuqu group sample. Full article

In this study, we aimed to isolate and phenotypically characterize non-Saccharomyces yeast strains (NSYSs) from the skin of aromatic (Italy) and non-aromatic (Negra Criolla) grapes from vineyards in Moquegua, Peru, typically used for the production of pisco. Our second objective was to characterize the volatile compounds and sensory attributes of pisco made from these grapes. Pichia terricola (56%), Metschnikowia pulcherrima (31%), and Naganishia vaughanmartiniae (13%) were the main NSYSs isolated from the skin of aromatic Italy grapes and identified; meanwhile, Vishniacozyma carnescens (50%), Vishniacozyma heimaeyensis (30%), and Aureobasidium pullulans (20%) were identified on the skin of the non-aromatic Negra Criolla grapes. These NSYSs showed different capacities in terms of carbohydrate fermentation, polygalacturonase activity, ethanol tolerance, sulphite production, and nitrogen consumption. Moreover, the pisco resulting from these varieties of grape had different volatile profiles. Terpene alcohols such as citronellol, geraniol, linalool, and nerol were found in pisco made from Italy grapes, while higher contents of 2-phenylacetate and ethyl esters were found in Negra Criolla Pisco. Intermediate levels of both 1-hexanol and bencyl alcohol were also found in all the pisco. Sensory analysis performed by a trained pisco tasting panel showed that citric, floral, alcohol, and syrup descriptors were more marked in Italy Pisco, while nuts, syrup, alcohol, and floral were the most intense attributes of Negra Criolla Pisco. These results will contribute to determining the potential of indigenous grape yeasts from the Moquegua region as fermentation starters to improve the typical sensory qualities of the pisco produced in this region, which deserves further study. Full article

Polyphenols are important functional substances produced in the acetic acid fermentation (AAF) of Shanxi aged vinegar (SAV). Previous studies have shown that the metabolic activity of microorganisms is closely related to polyphenol production and accumulation. In this study, microorganisms in the AAF of SAV were analyzed to explore how to increase the polyphenol yield by changing the microorganisms and reveal the potential mechanism of the microbial influence on the polyphenol yield. Macrotranscriptome analysis showed that acetic and lactic acid bacteria dominated the AAF fermentation process and initially increased and decreased. Spearman correlation analysis and verification experiments showed that the co-addition of Acetobacter pasteurianus and Lactobacillus helveticus promoted the accumulation of polyphenols, and the total polyphenol content increased by 72% after strengthening. Full article

Modern society is characterised by its outstanding capacity to generate waste. Lignocellulosic biomass is most abundant in nature and is biorenewable and contains energy sources formed via biological photosynthesis from the available atmospheric carbon dioxide, water, and sunlight. It is composed of cellulose, hemicellulose, and lignin, constituting a complex polymer. The traditional disposal of these types of waste is associated with several environmental and public health effects; however, they could be harnessed to produce several value-added products and clean energy. Moreover, the increase in population and industrialisation have caused current energy resources to be continuously exploited, resulting in the depletion of global fuel reservoirs. The overexploitation of resources has caused negative environmental effects such as climate change, exacerbating global greenhouse gas emissions. In the quest to meet the world’s future energy needs and adequate management of these types of waste, the anaerobic digestion of lignocellulosic biomass has remained the focus, attracting great interest as a sustainable alternative to fossil carbon resources. However, substrate characteristics offer recalcitrance to the process, which negatively impacts the methane yield. Nevertheless, the biodigestibility of these substrates can be enhanced through chemical, physical, and biological pretreatment methods, leading to improvement in biogas yields. Furthermore, the co-digestion of these substrates with other types and adding specific nutrients as trace elements or inoculum will help to adjust substrate characteristics to a level appropriate for efficient anaerobic digestion and increased biogas yield. Full article

Every year, seafood waste produced globally contains about 10 million tons of wasted crab, shrimp and lobster shells, which are rich in chitin resources. The exploitation and utilization of chitin resources are of great significance to environmental protection, economic development and sustainable development. Lytic polysaccharide monooxygenases (LPMOs) can catalyze polysaccharides by oxidative breakage of glycosidic bonds and have catalytic activity for chitin and cellulose, so they play an important role in the transformation of refractory polysaccharides into biomass. Although there have been many studies related to LPMOs, the research related to lytic chitin monooxygenases (LCMs) is still very limited. The specific catalytic mechanism of LCMs has not been fully elucidated, which poses a challenge to their application in industrial biomass conversion. This review introduces the present situation of resource development and utilization in chitin, the origin and classification of different LCMs families, the structural characteristics of LCMs and the relationship between structure and function. The research results related to activity detection, screening, preparation and transformation of LCMs were summarized and discussed. Finally, the synergistic effect of LCMs and chitin enzyme on biomass degradation was reviewed, and the existing problems and future research directions were pointed out. This is the first review focusing on Chitin-Active LPMOs in recent years, intending to provide a reference for applying chitin degradation enzymes system in the industry. Full article

This study aimed to investigate the effects of ultra-long-term fermentation on the formation of non-volatile metabolites of Chinese solid-fermented kohlrabies. Liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) based non-targeted metabolomics coupled with multivariate statistical analysis were employed to respectively analyze the kohlrabies solid fermented for 5 years (5Y), 8 years (8Y), and 11 years (11Y). The results showed that 31, 169, and 123 differential metabolites were identified in the three groups of 5Y and 8Y (A1), 5Y and 11Y (A2), and 8Y and 11Y (A3), respectively (VIP > 1, p < 0.05 and |log₂FC| > 1). The differential non-volatile metabolites were mainly organic acids and derivatives, organoheterocyclic compounds, benzenoids, lipids and lipid-like molecules, and organicoxygen compounds. Furthermore, 11 common differential metabolites were screened in the three groups, including diaminopimelic acid, ectoine, 9,10,13-TriHOME, and 9 others. The citrate cycle, glycine, serine and threonine metabolism, pantothenate and CoA biosynthesis, and glyoxylate and dicarboxylate metabolism were the four pathways most significantly correlated with the differential non-volatile metabolites based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis (p < 0.05). The present study describes the effects of ultra-long-term fermentation periods on the formation of non-volatile metabolites in solid fermented kohlrabies, providing a theoretical basis for cooking with the three solid fermented kohlrabies to make different Chinese dishes. Full article

Antibiotics have been detected in tiny environmental matrices all over the world, which caused a lot of concern. To solve this problem, biological treatment can be a low-cost and high-efficiency way. The use of biochar adsorbents made from the residual sludge of sewage for wastewater treatment can achieve pollutant removal while realizing pollutant reduction and reuse, which is of great significance for green development. In this study, a prepared biochar-based adsorbent (PBA) was modified and used for norfloxacin (NOR) removal. The composition of the adsorbent was characterized, and the influence of application factors on adsorption performance was investigated. After being modified and optimized, an overall removal efficiency of 84% was achieved for NOR in 4 h. The adsorption behavior was spontaneous and consistent with the Lagergren pseudo-second kinetic model and Langmuir model. The adsorption capacity of PBA reached 8.69 mg·L⁻¹ for NOR. A total removal efficiency of 62% was obtained for five mixed quinolone antibiotics by PBA. The PBA could be well regenerated and reused five times. This study explored a new method of the bio-waste utilization of sewage sludge for antibiotic removal from wastewater. Full article

The aim of the study was to analyze the effect of a plant feed additive based on Artemisia absinthium and the metal trace element CoCl₂ (cobalt chloride II) on the metabolism of amino acids closely related to the energy of feed and the bacterial community of the rumen of Kazakh white-headed bulls. Animals were divided into four groups: (A)—the control group of animals received the basic diet (BD), (B)—animals of the experimental group I were additionally given A. absinthium at a dose of 2.0 g/kg of dry matter (DM), (C)—II experimental group A. absinthium at a dose of 2.0 g/kg DM with additional CoCl₂ (1.5 mg/kg/DM), and (D)—III experimental group was given only CoCl₂ (1.5 mg/kg/DM) to study the rumen metabolism of amino acids and bacterial diversity of animals, rumen cannula were installed, the experiment was carried out using a 4 × 4 Latin square. It was found that additional feeding of A. absinthium, both separately and in combination with CoCl₂, led to a change in the indices of the alpha biodiversity of the bacterial community. Correlation analysis revealed a linear relationship between the concentration of amino acids and the rumen bacterial community (p ≤ 0.05). The relationship between the values of amino acid concentrations and certain OTUs was established, with a possible percentile probability of 95% for the genera unclassified Lachnospiraceae, unclassified Clostridiales, unclassified Bacteroidales, Fibrobacter, Ihubacter, Phocaeicola, Paludibacter, Akkermansia, Vampirovibrio, unclassified Ruminococcaceae, and Alistipes. Thus, the use of A. absinthium and CoCl₂ as feed additives, both in combination and without, leads to a change in the taxonomic structure affecting the concentration of amino acids. However, further research is needed to better understand the effectiveness and safety of these supplements. Full article

With the current increase in demand for animal and agricultural products, management of agrowaste has become critical to avoid greenhouse gas emissions. The present article investigates the applicability of ammonium bicarbonate synthesis via flash distillation to valorize and stabilize several types of anaerobic digestates which are produced from individual fermentations of amino acids. The content of CO₂ in the digestate was found to be responsible for the OH alkalinity (0.4 equivalents of acid/kg digestate), while the partial and total alkalinities (0.8 eq/kg digestate) were essentially derived from the content of NH₃. The most suitable conditions for the flash distillation were 95 °C and 1 bar with the condensation occurring at 25 °C. However, in order to attain the precipitation of NH₄HCO₃ in the distillate, it was necessary to consider digestates with a moisture content of 50 wt.%, since saturation levels of inorganic nitrogen and inorganic carbon were not attained otherwise. Even under these conditions, few amino acids (i.e., arginine, glycine, and histidine) were able to provide an anaerobic digestate upon fermentation that would be suitable for NH₄HCO₃ stabilization. The process of stabilization with a capacity of a t of digestate per h was improved by adding hydrochloric acid or sodium hydroxide at a rate of 44 kg/h, leading to production of 34 kg NH₄HCO₃/h. Given the role of the volatile elements of the biogas as endogenous stripping agents, it is recommended to use a fresh and saturated digestate as feed for the flash distillation. Full article

D-Tagatose is a low-calorie sugar substitute that has gained increased attention as a functional sweetener owing to its nutraceutical and prebiotic properties. Traditionally, D-tagatose is produced via the enzymatic conversion of L-galactose to D-tagatose by L-arabinose isomerase (L-AI). Nonetheless, the most reported L-AI enzymes are ion-dependent enzymes requiring Mn²⁺ and/or Co²⁺ as cofactors for their reactions, which limits their application due to safety and health concerns. Herein, we addressed the facile bioconversion of L-galactose to D-tagatose using a novel recombinant metallic-ions-independent L-AI derived from endophytic Bacillus amyloliquefaciens CAAI isolated from cantaloupe fruits. The ORF (1500 bp) of the L-arabinose isomerase gene (araA) was cloned and over-expressed in Escherichia coli. The recombinant enzyme (BAAI) was purified to homogeneity using Ni-NTA affinity chromatography, yielding a single distinct band with an apparent molecular mass of approximately 59 kDa as deduced from SDS-PAGE analysis. The purified enzyme showed optimum activity at pH and temperature of 7.5 and 45 °C, respectively, with obvious enzymatic activity in the presence of ethylenediaminetetraacetic acid (EDTA), indicating the metallic-ions independence from BAAI. The K_m values of BAAI for D-galactose and L-arabinose were 251.6 mM and 92.8 mM, respectively. The catalytic efficiency (k_cat/K_m) values for D-galactose and L-arabinose were found to be 2.34 and 46.85 mM^–1 min^–1, respectively. The results revealed the production of 47.2 g/L D-tagatose from D-galactose (100 g/L) with 47.2% bioconversion efficiency in a metallic-ions-free reaction system that could be implemented in safe-production of food-grade low-calorie sweetener, D-tagatose. Full article