The use of cottonseed hulls as a feed resource is constrained by their high fiber content and residual free gossypol. This study evaluated the effects of steam explosion combined with fermentation using a microbial–enzyme preparation on the nutrient composition, fermentation quality, bacterial communities, and in vitro digestion and fermentation characteristics of cottonseed hulls. Four treatments were evaluated using physicochemical analyses, 16S rRNA gene sequencing, and in vitro incubation: an untreated control (CK), steam explosion (BP), fermentation with a microbial–enzyme preparation (FJ), and steam explosion followed by fermentation with the same preparation (BF). All processing treatments significantly reduced free gossypol content (p < 0.05), with BF showing the lowest concentration (70.42 mg/kg), representing a 77.89% reduction relative to CK. The neutral detergent fiber (NDF) and acid detergent fiber (ADF) contents of BF were 573.38 and 446.23 g/kg dry matter (DM), respectively, both significantly lower than those of CK (p < 0.05) but not significantly different from those of BP. Crude protein content did not differ significantly among treatments. BF had the highest lactic acid content (27.94 g/kg DM) and the lowest endpoint pH (4.12). Bacterial community analysis showed that Firmicutes was the dominant phylum in all three fermented groups. At the end of fermentation, Lentilactobacillus was the dominant genus in the BF group, with a relative abundance of 97.55%. No associations between bacterial taxa and fermentation parameters remained significant after correction for multiple testing. KEGG functional prediction indicated differences in potential functional composition among treatments. In vitro DM digestibility in BF reached 43.99% at 48 h; however, NDF digestibility did not differ significantly among treatments at any incubation time. Cumulative gas production and total volatile fatty acid concentration in BF at 48 h were 154.28 mL/g DM and 64.58 mmol/L, respectively, neither of which differed significantly from FJ. In conclusion, steam explosion combined with microbial–enzyme fermentation reduced free gossypol content, promoted lactic acid accumulation, and altered bacterial community composition, providing experimental evidence to support further development of cottonseed hulls as a feed resource.
Spontaneous fermentations contribute to the identity of ancestral mezcal, although duration and yield may vary. This study selected an indigenous yeast and evaluated it as a starter candidate. Four native isolates (Torulaspora delbrueckii A1GM and A6GM, Kluyveromyces marxianus A2GM, and Saccharomyces cerevisiae A5GM) and a spontaneous control were compared in Agave cupreata microfermentations. Selection considered distillate alcohol content and preliminary ethanol-tolerance assays. A5GM was subsequently evaluated in three production batches containing A. angustifolia + A. karwinskii, A. angustifolia, or A. cupreata + A. angustifolia, with three independent vats per treatment. Fermentation profiles, distillate composition, yield, and sensory acceptance were assessed. A5GM produced the highest microfermentation distillate alcohol content (43.91 ± 0.89% Alc. Vol.) and grew at 16% ethanol (v/v). In the first two production batches, inoculated vats showed higher volumes standardized to 45% Alc. Vol. and lower calculated agave requirements than the controls; these were batch-specific observations under the operating conditions studied. Sensory evaluation used pooled vat-derived distillate composites, and the A5GM composites received the highest mean hedonic scores. Because strain-level establishment and persistence of A5GM were not confirmed, the observed outcomes cannot be attributed exclusively to this strain. Sensory interpretation is limited by fixed presentation order. Further independent batches, standardized management, and strain-level monitoring are needed to assess reproducibility.
Increasing the solids concentration in farm dairy effluent is necessary to operate a biogas plant at optimal parameters; however, conventional chemicals reduce CH4 production. This study evaluated the effects of the tannin-based coagulant–flocculant Tanfloc SG® on anaerobic digester performance using biomethane potential (BMP) tests with centrifuged solids produced at 50–300 mg Tanfloc g TS−1, and semi-continuous fermentation tests with settled solids at 150 mg g TS−1 (Tanfloc150). In the fermentation tests, the control and Tanfloc-treated solids were fed into two reactors, operating at 37 °C, at 2.1 kg VS m−3 d−1 with a 12- to 15-day hydraulic retention time. In the BMP tests, the Tanfloc-treated solids showed delayed degradation and produced 168.2–303.1 L CH4 kg VS−1, values not significantly different from the untreated solids (250.0 L CH4 kg VS−1). However, semi-continuous feeding reduced the volatile solids degradation, biogas, and specific CH4 yield by 23.3%, 17.9%, and 24.1%, while the pH, volatile fatty acids, and ammonia-N remained stable. However, Tanfloc150 reduced the biogas H2S and NH3 concentrations and increased the digestate N and S. The lower performance was associated with lower substrate biodegradability, which was consistent with the delayed degradation observed in the BMP tests. These findings highlight the importance of assessing coagulated solids under conditions representative of long-term performance.
Rhamnolipids are promising biosurfactants with diverse applications, but their efficient production from glucose remains challenging. In this study, a glucose-based fermentation process was developed using Pseudomonas aeruginosa YM4 through sequential evaluation of nitrogen source, pH, C/N ratio, glucose concentration, and Fe2+ supplementation in a 5 L bioreactor. A mixed NH4+/NO3− nitrogen source resulted in higher rhamnolipid production than either NH4+ or NO3− alone. Maintaining the culture pH at 7.2 prevented excessive acidification and promoted glucose consumption and rhamnolipid production. The highest rhamnolipid titer (29.7 g/L) was achieved using 100 g/L glucose, a C/N ratio of 35, and 10.8 μM Fe2+. Fermentation kinetics indicated that biomass accumulated rapidly during the early fermentation stage, whereas rhamnolipid production continued after cell growth had slowed. Under the selected conditions, YM4 produced a rhamnolipid mixture containing 73.8% di-rhamnolipids and showed substantially higher rhamnolipid production than three additional P. aeruginosa strains cultivated under identical conditions. This study developed a glucose-based fermentation process for producing di-rhamnolipid-rich products and demonstrated the efficient rhamnolipid-producing capability of P. aeruginosa YM4 under the evaluated conditions.
Lactic acid bacteria combining probiotic properties with acidification capacity and stress tolerance are valuable for food fermentation but remain insufficiently characterized. In this study, a strain of Pediococcus acidilactici, designated PA-X1, was isolated from pastoral fermented yak yogurt collected from the Qinghai–Tibet Plateau. Its in vitro probiotic-related properties, acidification performance, genomic characteristics, and expression patterns of key genes associated with acidification-related metabolism were investigated. After 24 h of fermentation, the broth pH decreased to 3.75 ± 0.02 and the L-lactic acid concentration reached 8.53 ± 0.23 g/L. The glucose concentration decreased from the measured initial value of 20.0 g/L at 0 h to 6.00 g/L at 24 h, corresponding to 70.0% glucose consumption. PA-X1 showed a survival rate of 94.64 ± 0.10% at pH 3.0, and its culture supernatant inhibited all three tested indicator bacteria, namely Escherichia coli, Salmonella enterica, and Staphylococcus aureus, in vitro. Genomic analysis identified multiple genes associated with acidification-related metabolism, including those involved in the phosphotransferase system (PTS), the Embden–Meyerhof–Parnas pathway, pyruvate metabolism and lactate synthesis. Additionally, the PTS-related genes ptsI, ptsH, and crr were significantly upregulated under high-glucose conditions (40 g/L), whereas low-pH conditions induced varying degrees of upregulation of glycolysis- and pyruvate-metabolism-related genes, including pgk, eno, tpiA, ldhA, ldhL, and ackA. Together, these phenotypic, genomic, and gene-expression results suggest that the acidification phenotype of PA-X1 may be associated with carbohydrate uptake, glycolysis, pyruvate metabolism, and organic acid formation. Overall, the combined probiotic-related, acidification, and antibacterial properties of PA-X1 support its potential as a functional starter culture for developing probiotic fermented foods with improved microbial safety and functional value.
