Adding value to rice straw waste for high-level xylanase production using a new isolate of Bacillus altitudinis RS3025

Valorization of lignocellulosic wastes for sustainable xylanase production from locally isolated Bacillus subtilis exploited for xylooligosaccharides' production with potential antimicrobial activity

The worldwide availability of lignocellulosic wastes represents a serious environmental challenge with potential opportunities. Xylanases are crucial in lignocellulosic bio-hydrolysis, but the low enzyme productivity and stability are still challenges. In the current study, Bacillus subtilis (coded ARSE2) revealed potent xylanase activity among other local isolates. The enzyme production optimization revealed that maximum enzyme production (490.58 U/mL) was achieved with 1% xylan, 1.4% peptone, and 5% NaCl at 30 °C and pH 9. Furthermore, several lignocellulosic wastes were exploited for sustainable xylanase production, where sugarcane bagasse (16%) under solid-state fermentation and woody sawdust (2%) under submerged fermentation supported the maximum enzyme titer of about 472.03 and 485.7 U/mL, respectively. The partially purified enzyme revealed two protein bands at 42 and 30 kDa. The partially purified enzyme revealed remarkable enzyme activity and stability at 50-60 °C and pH 8-9. The enzyme also revealed significant stability toward tween-80, urea, DTT, and EDTA with Vmax and Km values of 1481.5 U/mL and 0.187 mM, respectively. Additionally, the purified xylanase was applied for xylooligosaccharides production, which revealed significant antimicrobial activity toward Staphylococcus aureus with lower activity against Escherichia coli. Hence, the locally isolated Bacillus subtilis ARSE2 could fulfill the xylanase production requirements in terms of economic production at a high titer with promising enzyme characteristics. Additionally, the resultant xylooligosaccharides revealed a promising antimicrobial potential, which paves the way for other medical applications.

Genome sequence analysis and characterization of Bacillus altitudinis B12, a polylactic acid- and keratin-degrading bacterium

Keratin-rich wastes, mainly in the form of feathers, are recalcitrant residues generated in high amounts as by-products in chicken farms and food industry. Polylactic acid (PLA) is the second most common biodegradable polymer found in commercial plastics, which is not easily degraded by microbial activity. This work reports the 3.8-Mb genome of Bacillus altitudinis B12, a highly efficient PLA- and keratin-degrading bacterium, with potential for environmental friendly biotechnological applications in the feed, fertilizer, detergent, leather, and pharmaceutical industries. The whole genome sequence of B. altitudinis B12 revealed that this strain (which had been previously misclassified as Bacillus pumilus B12) is closely related to the B. altitudinis strains ER5, W3, and GR-8. A total of 4056 coding sequences were annotated using the RAST server, of which 2484 are core genes of the pan genome of B. altitudinis and 171 are unique to this strain. According to the sequence analysis, B. pumilus B12 has a predicted secretome of 353 proteins, among which a keratinase and a PLA depolymerase were identified by sequence analysis. The presence of these two enzymes could explain the characterized PLA and keratin biodegradation capability of the strain.