Genome assisted probiotic characterization and application of Bacillus velezensis ZBG17 as an alternative to antibiotic growth promoters in broiler chickens.

The present study describes genome annotation and phenotypic characterization of Bacillus velezensis ZBG17 and evaluation of its performance as antibiotic growth promoter substitute in broiler chickens. ZBG17 comprises 3.89 Mbp genome with GC content of 46.5%. ZBG17 could tolerate simulated gastrointestinal juices prevalent in the animal gut. Some adhesion-associated genomic features of ZBG17 supported the experimentally determined cell surface hydrophobicity and cell aggregation results. ZBG17 encoded multiple secondary metabolite gene clusters correlating with its broad-spectrum antibacterial activity. Interestingly, ZBG17 completely inhibited Salmonella enterica and Escherichia coli within 6 h and 8 h in liquid co-culture assay, respectively. ZBG17 genome analysis did not reveal any genetic determinant associated with reported safety hazards for use as a poultry direct-fed microbial. Dietary supplementation of ZBG17 significantly improved feed utilization efficiency and humoral immune response in broiler chickens, suggesting its prospective application as a direct-fed microbial in broiler chickens.

Exploration of a cheaper carbon source for extracellular ß-glucosidase synthesis from Debaryomyces pseudopolymorphus NRRL YB-4229.

In the present work, interactions between common media components and fermentation conditions were explored to come up with a simple media recipe for extracellular ß-glucosidase (Dß-gl) synthesis from Debaryomyces pseudopolymorphus to substitute cellobiose, which is currently used as a sole carbon source. Taguchi L25 orthogonal array design was used to screen factors influencing Dß-gl synthesis (carbon, organic nitrogen, inorganic nitrogen, trace elements, inoculum volume, and fermentation time). A significant influence of xylose, peptone, and potassium nitrate as carbon, organic nitrogen, and inorganic nitrogen sources, respectively, on Dß-gl synthesis was identified by Taguchi. These factors were further optimized using central composite rotatable design (CCRD) of response surface methodology (RSM). The results showed that in the range studied, potassium nitrate had insignificant effect while xylose, peptone, and xylose-peptone interaction had a significant effect on Dß-gl synthesis. Peptone/xylose ratio of 1.33 was found to be an important parameter for inducing Dß-gl synthesis. The regression coefficient (R (2)) of 0.915 and P value of <0.0003 for the model indicated that it was highly significant. The maximum activity obtained after RSM (32.2 U/ml) was comparable with that obtained (68.8 U/ml) when cellobiose (20 g/l) was used as a sole carbon source. Considering the cost difference between xylose and cellobiose, a 16-fold cost reduction could be obtained for equivalent Dß-gl yield. Fed-batch fermentations were carried out wherein peptone/xylose ratio of 1.33 was maintained and continuous Dß-gl synthesis was observed.