Mycoprotein is an alternative protein produced through fungal fermentation. However, it typically relies on refined glucose syrup derived from starch, which can be costly and unsustainable. This study investigates the potential of soybean processing by-products (okara and soy whey) as alternative substrates for producing mycoprotein using Aspergillus oryzae. A. oryzae was cultured for 7 days at 30 °C in diluted okara (1:50) and soy whey (1:1) with or without agitation (100 rpm). Soy whey produced higher biomass yields (369.2–408.8 mg dry biomass/g dry substrate), but had a lower biomass concentration (0.783–0.867 g dry weight/L). Conversely, okara produced a higher biomass concentration (2.02 g dry weight/L) with a yield of 114.7 mg dry biomass/g dry substrate. However, biomass formation in okara was only observed in static conditions, as agitation caused biomass to entangle with soy pulp, hampering its production. Additionally, okara tended to release protein into the media, while soy whey accumulated protein within the biomass, reaching up to 53% w/w protein content. The results of this study provide a promising approach to addressing both soybean processing waste reduction and food security concerns.

Pediococcus acidilactici has gained research and commercial interest due to its outstanding probiotic properties, yet its survival during storage and consumption requires improvement. This study aims to enhance P. acidilactici survival using spray drying encapsulation. Different inlet air temperatures (120 °C, 150 °C, and 170 °C) and whey protein isolate (WPI):gum arabic (GA) ratios (1:1, 3:1, 1:3) were tested. Cell viability was significantly (p < 0.05) affected by the inlet temperature but not the WPI:GA ratio. Increasing the inlet temperature to 170 °C significantly decreased P. acidilactici viability by 1.36 log cycles, from 8.61 log CFU/g to 7.25 log CFU/g. The inlet temperature of 150 °C resulted in a powder yield (63.12%) higher than at 120 °C (58.97%), as well as significantly (p < 0.05) lower moisture content (5.71%) and water activity (a_w 0.21). Viable cell counts in all encapsulated P. acidilactici were maintained at 5.24–6.75 log CFU/g after gastrointestinal tract (GIT) simulation, with WPI:GA of 3:1 and inlet temperature 150 °C having the smallest log reduction (0.3 log cycles). All samples containing different WPI:GA ratios maintained sufficient viability (>7 log CFU/g) during the first three weeks of storage at 25 °C. These results could provide insights for further developing P. acidilactici as commercial probiotic products.

This study delves into the production and antimicrobial characteristics of cell-free supernatants from Pediococcus acidilactici (CFSs-Pa). Antimicrobial activity was initially observed in CFS-Pa harvested after 12 h of incubation and increased up to the late stationary phase at 48 h. The increase in antimicrobial activity did not align with total protein content, pointing to other factors linked to the accumulation of organic acids, particularly lactic acid. The SDS-PAGE analysis also indicated that the expected proteinaceous compound (pediocin) was not observed in CFS-Pa. Further investigations suggested that the antimicrobial properties of CFS-Pa were exclusively due to organic acids. The MIC values confirmed potent antimicrobial activity, particularly at a 10% dilution of CFS-Pa in MRS broth. The time–kill assays demonstrated bactericidal activity against EHEC, Listeria monocytogenes, and Staphylococcus aureus by 12 h, 18 h, and 24 h using a 10% dilution of CFS-Pa. Additionally, CFS-Pa exhibited dose-dependent antioxidant activity, requiring a 70% (v/v) concentration to inhibit DPPH scavenging activity by 50%. All the experimental results suggested potential applications of CFS-Pa in food preservation. An attempt to incorporate CFS-Pa into bacterial cellulose (BC) for edible food packaging demonstrated promising antimicrobial results, particularly against L. monocytogenes and S. aureus, with room for optimization.

Probiotics are live microorganisms that can confer health benefits when consumed in sufficient amounts. However, probiotics are often subjected to various temperature stresses during their processing and storage, which may lead to undesirable loss of viability. Pediococcus acidilactici, a species of lactic acid bacteria, is a promising probiotic candidate due to its ability to produce the antimicrobial peptide pediocin. Their response to temperature-related stress, especially at the molecular level, is still poorly understood. This study investigated the effect of shocks at various temperatures on the viability and stress-related gene expression of P. acidilactici. There was no significant reduction in the viability of P. acidilactici after temperature shock for 5 minutes at -80°C, 4°C, and 60°C compared to the control at 30°C (Log 9.2-9.3 CFU/mL), while there was a significant reduction in the culture subjected to 75°C (Log 6.17) and 90°C (0), both for 5 mins. RT-qPCR analysis showed no significant differences in the expression of groEL, a heat shock response gene, in P. acidilactici subjected to -80°C, 4°C, and 60°C compared to 30°C, although possible gDNA contamination might occur. These results suggest that P. acidilactici potentially has good survival when subjected to heat-based food processing for probiotics product development.

Soy sauce is a condiment made of soybeans fermented in high salt concentration (18-22% NaCl) called moromi. Efforts to prevent sodium overconsumption has led to salt reduction in moromi. However, it could alter the microbial community dynamics during fermentation, resulting in undesirable sensory changes. This study investigates the effect of moromi starter cultures, Tetragenococcus sp. and Zygosaccharomyces rouxii, on microbial population changes during reduced-salt moromi (6% NaCl) fermentation. Both microbes were inoculated at different times, concentrations, and ratios, and the changes in total bacterial and yeast population during fermentation were monitored by culture on tryptic soy agar (TSA) and potato dextrose agar (PDA), respectively. The results showed that the inoculum size could shorten the bacterial exponential growth as it increased. Moreover, increasing the proportion of Tetragenococcus or Z. rouxii by two-fold could enhance the yeast and bacterial population, respectively by ∼3 log CFU/mL. Simultaneous inoculation suppressed bacterial growth, while sequential inoculation of Z. rouxii could maximize bacterial growth up to 7.38 log CFU/mL. However, a synergistic growth in simultaneous inoculation was observed when 5% inoculum with an equal ratio was used. This study could help researchers and manufacturers determine appropriate inoculation procedures to control fermentation better.