ABSTRACT
Abstract The bacteria residing in the gut of honey bees (HB) has demonstrated a significant role in protecting bees against various pathogens, production of honey and wax. However, no information exists about the antibacterial potential of bacterial isolates from gut of Asian HB, Apis cerana Indica F. (Hymenoptera: Apidae), against human pathogens. This study aims to investigate the antibacterial and multienzyme potential of aerobic bacteria from A. cerana gut using culture dependent approach. A total of 12 HB gut bacteria were characterized morphologically and biochemically. These strains were further screened for their antimicrobial activity against pathogenic human microorganisms Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumonia, Bacillus licheniformis and Bacillus subtilis using cross streak (primary screening) and agar well diffusion methods (secondary screening). Preliminary characterization of cell-free supernatant (CFS) of two promising isolates was performed by measuring lactic acid concentrations, enzymatic digestion of antimicrobial compounds, stability over a range of temperature, pH and amplification of spaS (subtilin) and spoA (subtilosin) genes. In primary screening, among 12 HB isolates, eight strains showed statistically significant highest zones of inhibition (p≤0.05) against E. coli, K. pneumoniae and P. aeruginosa. 16S rRNA sequencing revealed that these isolates belong to Bacillus genus, identified as B. tequilensis, B. pumilus, B. xiamenensis, B. subtilis, B. amyloliquefaciens, B. safensis, B. licheniformis, B. altitudinis (Accession numbers: MT186230-MT186237). Secondary screening revealed that among eight isolates, B. subtilis and B. amyloliquefaciens showed statistically significantly strong inhibition (p≤0.05) against all tested pathogens. Antibiotic susceptibility testing revealed that both isolates were resistant to antibiotics and possesses proteolytic, lipolytic and cellulolytic activities. The nature of the compound causing inhibitory activity was found to be proteinaceous and showed stability over a wide range of temperature as well as pH. PCR study confirmed the presence of bacteriocins by successful amplification of important antimicrobial peptide biosynthesis genes spaS and spoA. These results suggest that the HB gut is a home to bacteria that possess antimicrobial activity and important enzymes with antimicrobial potential. To our knowledge, this is the first report demonstrating the antimicrobial potential of bacteria isolated from gut of HB (A. cerana) against human pathogens.
ABSTRACT
Xylanases are in the focus of research due to their potential to replace many current polluting chemical technologies by biochemical conversion. The field of application for xylanases is vast; it comprises industrial applications like wood pulp bio-bleaching, papermaking and bioethanol production. In addition, these enzymes can be applied as additives in food and beverage industry, and animal nutrition. However, considering the potential applications for these enzymes, the market share of xylanases is still low. Thus, the search for promising xylanases which tolerate relevant processing conditions and therefore can be used in industrial settings is an ongoing task. This review provides an overview of the enzymes reported from 2012 to mid 2014. Further, legal restrictions for the use of (genetically modified) organisms and enzymes are considered. This review provides an integrated perspective on the potential of specific xylanases for industrial applications.