Bacillus amyloliquefaciens 35 M can exclusively produce and secrete proteases when cultured in soybean-meal-based medium

Bacillus amyloliquefaciens CU33 Fermented Product Improves Growth Performance, Diarrhea, and Immunity of Goat Kids

This study focused on the physicochemical characteristics of the fermented products (FP) produced by Bacillus amyloliquefaciens CU33 (CU33) from soybean meal with 70% moisture. Additionally, it investigated the effects of adding FP to starter on the growth performance, general health performance, blood clinical biochemistry, and immunity of Alpine goat kids during the weaning period. Forty 14-day-old male Alpine goat kids were randomly assigned into starter supplementations of 0, 0.1, 0.3, or 0.5% CU33 FP for 8 weeks, and each goat kid was individually raised in stainless steel cage (width 70 cm × height 70 cm × depth 80 cm). The moisture after fermentation was linearly decreased as fermentation time increased (p < 0.05), and the pH value and Bacillus-like counts reached the highest at 24 h of fermentation. The activity of neutral protease and alkaline protease, the content of surfactin and γ-PGA, the viscosity, and the odor of CU33 FP were linearly increased as fermentation time increased (p < 0.05). The neutral protease activity, surfactin, γ-PGA, and viscosity increased after drying, whereas the moisture, pH value, Bacillus-like counts, and odor decreased (p < 0.05). During the pre-weaning period (0-4 weeks), the body weight gain (BWG) of the 0.1% CU33 FP group was higher than that of the control group (p < 0.05), and all CU33 FP groups showed a better feed conversion ratio (FCR) than the control group (p < 0.05). During the post-weaning period (4-8 weeks) and throughout the entire experimental period (0-8 weeks), the BWG and FCR of all CU33 FP groups were better than those of the control group (p < 0.05). Furthermore, both BWG and FCR improved linearly as the dietary level of CU33 FP increased (p < 0.05). Simultaneously, the fecal consistency index at 0-4 and 4-8 weeks and the coliform counts in the rectum at 4 weeks linearly decreased (p < 0.05), and the Bacillus-like counts in the rectum linearly increased at 4 and 8 weeks (p < 0.05). Phosphorous (P), total protein (TP), blood urea nitrogen (BUN) in serum at 8 weeks, and the oxidative burst capacity at 4 weeks linearly increased as the dietary level of CU33 FP increased, but the skin sensitization test showed a quadratic curve, and the 0.1% CU33 FP group had the lowest performance (p < 0.05). In conclusion, dietary supplementation with 0.1% of CU33 FP can improve the growth performance, diarrhea status, and oxidative burst capacity of Alpine goat kids, showing the potential to be a feed additive.

Characterization of the extracellular proteases from Bacillus inaquosorum strain E1-8 and its application in the preparation of hydrolysates from plant and animal proteins with antioxidant, antifreeze and anti-browning properties

BACKGROUND

Bacillus inaquosorum strains is widely recognized for their plant-growth-promoting and biocontrol capabilities, yet their roles in protease production remain unclear. The present study aimed to comprehensively assess the protease-producing performance of B. inaquosorum strain E1-8, at the same time as exploring the novel application of agricultural Bacillus proteases in the preparation of protein hydrolysates for fresh-cut fruits preservation.

RESULTS

First, genomic sequencing revealed the diversity of E1-8 proteases, indicating 15 putative extracellular proteases. Subsequently, the fermentation conditions for E1-8 protease production were optimized, with sweet potato powder and soybean meal identified as the most suitable carbon and nitrogen sources, respectively, resulting in a maximum protease activity of 321.48 U mL-1. Upon culturing the strain under these optimized conditions, only an S8 family serine protease and an M48 family metalloprotease were revealed by secretomic analysis and protease inhibitor assays. Additionally, the optimal protease conditions for generating protein hydrolysates from soy, pea, fish and porcine proteins were determined. The molecular weight of the hydrolysates primarily ranged from 2000 to 180 Da, with a total of 17 amino acids identified. The application of these hydrolysates demonstrated a 2,2-diphenyl-1-picrylhydrazyl (i.e. DPPH) scavenging activity ranging from 58.64% to 84.12%, significantly reducing of the melting peaks and the freezing points. Furthermore, the browning index of apple slices stored at 4 °C decreased by 14.81% to 22.15% on the second day, and similar effects were observed in fresh-cut banana stored at 4 °C for 7 days.

CONCLUSION

The protein hydrolysates obtained exhibit remarkable antioxidant, antifreeze and anti-browning properties for fresh-cut fruits. © 2024 Society of Chemical Industry.

Screening and Identification of a Strain with Protease and Phytase Activities and Its Application in Soybean Meal Fermentation

The aims of the study were to degrade the anti-nutritional factors (ANFs) such as phytic acid, glycinin, and β-conglycinin and improve the values of soybean meal (SBM). Firstly, in this study, a strain PY-4B which exhibited the best enzymatic activities of protease (403.3 ± 17.8 U/mL) and phytase (62.9 ± 2.9 U/mL) was isolated and screened among the isolates. Based on the analysis of physiological and biochemical characteristics and 16S rDNA sequence, the strain PY-4B was identified and named as Pseudomonas PY-4B. Next, Pseudomonas PY-4B was applied to fermentation of SBM. The results showed that the contents of glycinin and β-conglycinin were decreased by 57-63%, and the phytic acid was remarkably degraded by 62.5% due to the fermentation of SBM by Pseudomonas PY-4B. The degradation of glycinin and β-conglycinin resulted in increase of contents of water-soluble proteins and amino acids in fermented SBM. Moreover, Pseudomonas PY-4B exhibited no hemolytic activity and slight inhibitory effect on the growth of pathogen Staphylococcus aureus and the wide range of pH tolerance (3 to 9). In summary, our study indicates that isolated strain Pseudomonas PY-4B is a safe and applicable strain and has the ability to effectively degrade the ANFs (phytic acid, glycinin, and β-conglycinin) in SBM by fermentation.

Microbial proteases and their applications

Proteases (proteinases or peptidases) are a class of hydrolases that cleave peptide chains in proteins. Endopeptidases are a type of protease that hydrolyze the internal peptide bonds of proteins, forming shorter peptides; exopeptidases hydrolyze the terminal peptide bonds from the C-terminal or N-terminal, forming free amino acids. Microbial proteases are a popular instrument in many industrial applications. In this review, the classification, detection, identification, and sources of microbial proteases are systematically introduced, as well as their applications in food, detergents, waste treatment, and biotechnology processes in the industry fields. In addition, recent studies on techniques used to express heterologous microbial proteases are summarized to describe the process of studying proteases. Finally, future developmental trends for microbial proteases are discussed.