Four individual lactic acid bacteria strains (LABs), including Lactobacillus plantarum, Lactobacillus reuteri, Lactobacillus rhamnosus, and Pediococcus pentosaceus, were used for the fermentation of Kuqa apple juice (KAJ). This work investigated the effects of four individual LABs on physical and chemical and antioxidant properties of fermented KAJ. In addition, this study combined sensory evaluation to select one or two suitable strains for fermenting KAJ. The results showed that P. pentosaceus had the fastest speed for fermentation. The maximum SOD activity of L. plantarum reached 284.33 U/ml. The TPC of L. reuteri had a high value of 94.00 mg/L. The DPPH-free radical scavenging activity of L. plantarum eventually reached 97.90%, while the sensory evaluation of P. pentosaceus was the best with a 94% of GM value, followed by L. plantarum. Moreover, the major organic acid in fermented KAJ was malic acid. In summary, different strains have different effects on the characteristics of fermented KAJ, but in general, P. pentosaceus and L. plantarum are the most capable for fermenting KAJ. Novelty impact statement:The work provided the first research about malolactic fermentation for apples in Kuqa County, Xinjiang Province, China, which provided a new type of preservation technology for Kuqa apples and solved the problem of local apple with short storage period but high production. In addition, this work obtained the two most suitable strains for fermentation of Kuqa apple juice. In summary, this result provided a theoretical basis for the fermentation of Kuqa apple juice and enhanced economic benefits for the Kuqa apple industry. Highlights• This work research more than three kinds of individual lactic acid bacteria compared with other work.• There is no study about kuqa apple juice.The apples used come from Kuqa County, Xinjiang, China. As Kuqa County has sufficient sunlight and large temperature difference between day and night, the apples in Kuqa County are rich in nutrients and high in maturity.• This work belongs to bioengineering, so it plays an important role for the practical mean for apple industry. | MATERIAL S AND ME THODS | Materials, microbial strains, and enzymesTen kilograms of fresh apples were purchased from the fruit shop of Xinjiang University. Ethanol, gallic acid, and Folin-Ciocalteu phenol were got from Tianjin Shengao Chemical Reagent (Tianjin, China). The (DeMan, Rogosa and Sharpe) MRS culture medium were purchased from Beijing Aoboxing Biotechnology Co., Ltd. (Beijing, China). Lactobacillus plantarum, Lactobacillus reuteri, Lactobacillus rhamnosus, and Pediococcus pentosaceus were obtained from China Microbial Culture Preservation Center (Beijing, China). Pectinase, celluclast and hemicellulase were purchased from Novozymes, Ltd., China. The standard organic acids (tartaric acid, malic acid, lactic acid, citric acid, succinic acid, fumaric acid, and total organic acids) belong to HPLC grade. | CultivationThe strains were activated using the method described by Tang et al. ( 2017) with sight...

Sea buckthorn (Hippophae rhamnoides L.) is an edible and medicinal plant species. However, due to its sour taste, it is not readily accepted by consumers. To overcome this, fermentation can be used to change its flavor profile. In this study, we used response surface methodology (RSM) to determine the best process for producing fermented sea buckthorn juice (FSBJ) using probiotics. The biological enzyme activity and total flavonoid content (TFC) of sea buckthorn juice (SBJ) increased after fermentation. When the number of bacteria inoculated was 4.08 × 106 CFU/mL and the inoculation ratio was 30% Z. mobilis, 5% L. casei, 13.75% L. plantarum, 31.25% P. acidilactici, 12.5% L. animalis, and 7.5% P. pentosaceus, the amount of sugar was 2.98% (w/v) after 20 h of fermentation at 37°C, and the superoxide dismutase (SOD) activity reached 725.44 U/mL, and the TFC reached 2.38 mg/mL. FSBJ demonstrated strong antimicrobial activity against Escherichia coli, Staphylococcus aureus and Botrytis cinerea. Then, to investigate the antioxidant capacity of FSBJ, we used H2O2 to induce oxidative stress in C2C12 cells and assessed the protection conferred by FSBJ to damaged cells. It was discovered that after 24 h of treatment with FSBJ, not only was there an increase in the activities of intracellular SOD and glutathione peroxidase (GSH-Px), but also a reduction in reactive oxygen species (ROS) content, catalase (CAT) activity, and malondialdehyde (MDA) content. This research lays the theoretical groundwork and provides reference materials for the improved fermentation of sea buckthorn and demonstrates its resulting antioxidant effect.

Quinoa seeds are a food resource rich in protein, vitamins, minerals, and other functional components such as polyphenols, polysaccharides, and saponins. The seeds have become favored by modern consumers due to being gluten-free and featuring a high protein content. This study focused on the preparation of quinoa peptides by short-time enzymatic-assisted fermentation. Quinoa flour (QF) was mixed with water in a certain ratio before being enzymatically digested with 0.5% amylase and 0.1% lipase for 6 h. Then, 16 bacterial taxa were used for fermentation, respectively. The peptide content in the resulting fermentation broths were determined by the biuret method. The dominant taxon was then identified and the peptide content, amino acid distribution, and molecular weight distribution of the prepared quinoa peptides were analyzed. Further, the temperature, pH, metal ions, organic solvents, ion concentration, and anti-enzyme stability of the quinoa anti-hypertensive peptides of different molecular weights after fermentation with the dominant taxon were investigated. Finally, the inhibitory activity of fermented quinoa peptides on bacteria was studied. The results show that the peptide content of the fermentation broth reached 58.72 ± 1.3% at 40 h of fermentation with Lactobacillus paracasei and the molecular weights of the hydrolyzed quinoa peptides were mainly distributed below 2 kDa by polyacrylamide gel. The Angiotensin Converting Enzyme (ACE) inhibition and peptide retention of the 0–3 kDa quinoa peptides were screened to be high and stable. At the same time, the inhibitory activity of quinoa peptide after fermentation on E. coli was obvious. This study provides a theoretical basis for further research on quinoa peptide and its application in industrial production, and also lays a foundation for the later application of polypeptides in new food and chemical products.