Screening of Bacillus spp. bacterial endophytes for protease production, and application in feather degradation and bio-detergent additive.

Research on proteases and secondary metabolites from endophytes is an area that requires attention from researchers. In this study, proteases from Bacillus sp. strain MHSD16 and Bacillus sp. strain MHSD17 endophytes were characterised, and their potential biotechnological applications were investigated. Optimum protease production was achieved when isolates were grown in media containing (g/L): glucose 10g, casein 5g, yeast extract 5g, KH2PO4 2g, Na2CO3 10g at pH 9. The crude protease extracts were active in alkaline environments, thus referred to as alkaline proteases with optimal pH of 10. Additionally, Bacillus sp. strain MHSD 16 and Bacillus sp. strain MHSD17 proteases were active at high temperatures, with optimum enzyme activity at 50 °C. Thermostability profiles of these proteases showed that the enzymes were highly stable between (40-60 °C), maintaining over 85 % stability after 120 min incubation at 60 °C. Furthermore, the enzymes were stable and compatible with various household and laundry detergents. In the presence of commercial laundry detergent, OMO® 68 % and 72 % activity was retained for Bacillus sp. strain MHSD16 and Bacillus sp. strain MHSD17, respectively, while 67 % and 68 % activity were retained in the presence of Sunlight®. The potential application for use in detergents was investigated through the removal of blood stains with the crude alkaline extracts displaying efficient stain removal abilities. Feather degradation was also investigated and Bacillus sp. MHSD17 exhibited feather keratin degrading properties more effectively than Bacillus sp. MHSD16.

Analysis of the bacterial and fungal populations in South African sorghum beer (umqombothi) using full-length 16S rRNA amplicon sequencing.

There is a need to profile microorganisms which exist pre-and-post-production of umqombothi, to understand its microbial diversity and the interactions which subsequently influence the final product. Thus, this study sought to determine the relative microbial abundance in umqombothi and predict the functional pathways of bacterial and fungal microbiota present. Full-length bacterial 16S rRNA and internal transcribed spacer (ITS) gene sequencing using PacBio single-molecule, real-time (SMRT) technology was used to assess the microbial compositions. PICRUSt2 was adopted to infer microbial functional differences. A mixture of harmful and beneficial microorganisms was observed in all samples. The microbial diversity differed significantly between the mixed raw ingredients (MRI), customary beer brew (CB), and optimised beer brew (OPB). The highest bacterial species diversity was observed in the MRI, while the highest fungal species diversity was observed in the OPB. The dominant bacterial species in the MRI, CB, and OPB were Kosakonia cowanii, Apilactobacillus pseudoficulneus, and Vibrio alginolyticus, respectively, while the dominant fungal species was Apiotrichum laibachii. The predicted functional annotations revealed significant (p < 0.05) differences in the microbial pathways of the fermented and unfermented samples. The most abundant pathways in the MRI were the branched-chain amino acid biosynthesis super pathway and the pentose phosphate pathway. The CB sample was characterised by folate (vitamin B9) transformations III, and mixed acid fermentation. Biotin (vitamin B7) biosynthesis I and L-valine biosynthesis characterised the OPB sample. These findings can assist in identifying potential starter cultures for the commercial production of umqombothi. Specifically, A. pseudoficulneus can be used for controlled fermentation during the production of umqombothi. Likewise, the use of A. laibachii can allow for better control over the fermentation kinetics such as carbohydrate conversion and end-product characteristics, especially esters and aroma compounds.

Physicochemical Properties and Bacterial Community Profiling of Optimal Mahewu (A Fermented Food Product) Prepared Using White and Yellow Maize with Different Inocula.

Mahewu is a fermented food product from maize, commonly consumed in Southern Africa. This study investigated the effect of optimizing fermentation (time and temperature) and boiling time of white maize (WM) and yellow maize (YM) mahewu, with the use of the Box-Behnken-response surface methodology (RSM). Fermentation time and temperature as well as boiling time were optimized and pH, total titratable acidity (TTA) and total soluble solids (TSS) determined. Results obtained showed that the processing conditions significantly (p ≤ 0.05) influenced the physicochemical properties. pH values of the mahewu samples ranged between 3.48-5.28 and 3.50-4.20 for YM mahewu and WM mahewu samples, respectively. Reduction in pH values after fermentation coincided with an increase in TTA as well as changes in the TSS values. Using the numerical multi-response optimisation of three investigated responses the optimal fermentation conditions were observed to be 25 °C for 54 h and a boiling time of 19 min for white maize mahewu and 29 °C for 72 h and a boiling time of 13 min for yellow maize mahewu. Thereafter white and yellow maize mahewu were prepared with the optimized conditions using different inocula (sorghum malt flour, wheat flour, millet malt flour or maize malt flour) and the pH, TTA and TSS of the derived mahewu samples determined. Additionally, amplicon sequencing of the 16S rRNA gene was used to characterise the relative abundance of bacterial genera in optimized mahewu samples, malted grains as well as flour samples. Major bacterial genera observed in the mahewu samples included Paenibacillus, Stenotrophomonas, Weissella, Pseudomonas, Lactococcus, Enterococcus, Lactobacillus, Bacillus, Massilia, Clostridium sensu stricto 1, Streptococcus, Staphylococcus, Sanguibacter, Roseococcus, Leuconostoc, Cutibacterium, Brevibacterium, Blastococcus, Sphingomonas and Pediococcus, with variations noted for YM mahewu and WM mahewu. As a result, the variations in physicochemical properties are due to differences in maize type and modification in processing conditions. This study also discovered the existence of variety of bacterial that can be isolated for controlled fermentation of mahewu.