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In order to explore novel producing strategies for enhancing flavor compounds profile and quality of strawberry wine, we studied the effect of the sequential fermentation of two selected indigenous non-Saccharomycesyeasts (Hanseniaspora uvarumPGR9 and Kurtzmaniella quercitrusaPGT1) and Saccharomyces cerevisiaeCGMCC 2.3854 on the fermentation kinetics, physicochemical characteristics, organic acids, antioxidant activity, volatile compositions, and sensory properties. Results showed that the ethanol content produced by the fermentation of Kq-Scwas significantly lower than that of Scpure fermentation. In addition, the total volatile compounds concentration produced by the fermentation of Hu-Sc(16.2 ± 3.6 mg/L) and Kq-Sc(19.5 ± 3.1 mg/L) were significantly higher than that of Scpure fermentation (13.8 ± 2.0 mg/L). In particular, the Kq-Scstrawberry wine presented the highest number of relative odor-active compounds (rOAV ≥1). Moreover, strawberry wine fermented by Hu+Kq-Scshowed the highest ABTS free radical scavenging ability and the highest overall sensory qualities. The results indicated that the K. quercitrusaPGT1 strain could be an alternative yeast for producing strawberry wine, and the sequential fermentations of Kq-Sc and Hu+Kq-Scwere effective strategies for improving the flavor and quality of strawberry wine.

Peptide ferrous chelate is a new type of biological iron, which has the advantages of high absorption rate, safety and no digestive tract irritation. In this study, microbial fermentation was used for the first time to prepare iron-chelating peptides. Forty-eight strains were applied to ferment scallop skirts. A dominating strain was eliminated by using the iron binding capacity of the scallop skirt hydrolysate as the screening index. The scallop skirt hydrolysate fermented by Bacillus subtilisM17-b7 showed excellent iron-chelating capacity (96.20% ± 0.03%). Meanwhile, the structure, morphology and bioactivity of fermented scallop skirt hydrolysate (FSH) and fermented scallop skirt hydrolysate-iron (FSH–Fe) were measured. Based on the amino acid composition and spectral analysis, it was confirmed that the significant amino acids contains carboxyl, carbonyl, and amino groups. The result of scanning electron microscope indicated that the surface of FSH became porous and the particles were bigger after chelating with ferrous. Moreover, the peptide-ferrous chelate was more stable in salt solutions and simulated gastric juice compared with ferrous sulfate. It is also noteworthy that the preparation of ferrous chelate peptides by fermentation is cost-effective compared with enzymatic hydrolysis. Therefore, this study provides theoretical support for the use of fermentation as a promising tool to produce peptide-ferrous chelate.

Natto, a nutritious fermented soybean product, is known for its health benefits. Modern production methods use Bacillus subtilisas the starter culture to ensure consistent quality. However, this method overlooks the potential positive effects of other microbial species present in traditionally, naturally fermented natto. This study explored the effects of ARTP-induced mutants of B. subtilisvar. nattoand several strains of lactic acid bacteria (LAB) on natto quality. The results showed that these two types of bacteria have complementary roles in fermentation. B. subtilisvar. natto, with enhanced extracellular protease activity, promotes the hydrolysis of soy protein and enhances the product's ACE inhibitory and fibrinolytic activities. Meanwhile, two strains of Lactiplantibacillus plantarumreduced the content of total volatile basic nitrogen (TVB-N) while increasing the content of folic acid in the final product. In addition, B. subtilisvar. nattoand LAB produce different profiles of volatile compounds (VOCs). Subsequently, B. subtilisvar. nattoand Lpb. plantarumwere used to co-ferment natto in different ratios. The results showed that the two types of bacteria could co-colonize and enhance fermentation quality through their respective strengths. Specifically, Lpb. plantarumstrains co-metabolized with B. subtilisvar. nattoto elevate the content of pyrazines, characteristic VOCs in natto. The optimal quality of natto was achieved when Lpb. plantarumHIS6, Lpb. plantarumLP3 and B. subtilisvar. nattoY15-11 were combined in a 2:1:2 ratio. This study not only identified effective combinations of starter cultures with complementary benefits but also elucidated the metabolic pathways of key volatile compounds. Our findings also provide technical insights for improving natto quality, enhancing consumer acceptance, and supporting industrial production.

Kiwifruit, a climacteric-fruit susceptible to rapid deterioration, attains considerable value upon transformation into kiwifruit wine, thereby increasing its added value. However, a noteworthy challenge arises from its high pectin content, which negatively affects byproduct quality, necessitating pectinase treatment during processing. Commercial pectinases exhibit heightened pectin esterase activity, giving rise to safety apprehensions due to augmented methanol content during kiwifruit pectin hydrolysis. In this study, Bacillus velezensisW17-6 was screened for its high pectinase activity coupled with low pectin esterase activity. The resultant crude pectinase named PBV was acquired through fed-batch-fermentation and partial purification. Subsequently, PBV was deployed in the fermentation of Xuxiang kiwifruit wine, and its impact on overall quality was assessed through diverse analyses. The results indicated that Xuxiang kiwifruit wine with PBV treatment outperformed counterparts treated with commercial pectinases. PBV treatment not only yielded superior clarity (83.75%±0.47%) and juice yield (81.60%±0.47%) but also increased the total flavonoids content in Xuxiang kiwifruit wine by 1.2 times compared to commercial pectinase. Notably, the methanol content of PBV-treated Xuxiang kiwifruit wine was significantly lower at 36.13±1.83 mg/L than that of wines treated with two commercial pectinases. PBV-treated kiwifruit wine also exhibited elevated concentrations of volatile compounds such as phenethyl alcohol, ethyl undecanoate, lauric aldehyde, isobutyric acid, and myrcene. Impressively, PBV-treated kiwifruit wine surpassed other wines in both electronic and artificial sensory analyses. In summary, PBV exhibits substantial potential in the production of low-methanol, high-quality kiwifruit wine, enhancing the flavor and nutritional value while minimizing methanol production and improving the safety profile.

Ergothioneine (EGT) is a natural sulfur-containing amino acid with potent antioxidant and cytoprotective activities. In this study, the oxidation tolerance of 23 different Rhodotorulastrains were screened with hydrogen peroxide (H2O2) as the inhibitory condition. By measuring their carotenoid and EGT production and correlation analysis with H2O2tolerance, the results showed that the carotenoid synthesis capacity has no effect on H2O2tolerance, in contrast to a strong positive correlation between EGT yield and H2O2tolerance of Rhodotorulaspecies. In addition, a high EGT-producing strain R. mucilaginosaDL-X01 was screened with the yield of 38.48 ± 2.71 mg/L in a shaking flask fermentation. To the best of our knowledge, this is the highest EGT yield ever reported in non-recombinant strains. Growth kinetic data showed that DL-X01 had a longer lag phase in the presence of exogenous oxidant, but a shorter generation time and higher specific growth rate after entering the exponential phase. The results of this study provided a potential simple and rapid method for screening high EGT-producing strains, which could promote the efficient production of EGT by microorganisms and further development of the red yeast in the food and biotechnology industries.