Abstract
Thermophiles are excellent sources of enzymes that can withstand and carry out reactions efficiently under high temperatures. This study isolated and characterised thermotolerant bacteria that produce enzymes of potential industrial value from five hot springs in Eritrea. A total of 65 bacterial isolates were obtained from the five hot springs. Out of the 65 isolates; 19 isolates produced a positive reaction for amylases, 36 for carboxymethyl cellulases, eight for proteases, 10 for xylanases and 11 for pectinases. More than half (36 out of 65) were able to produce carboxymethyl cellulases. Six isolates which showed carboxymethyl cellulase activity were from the genus Bacillus, while those belonging to Brevibacillus were seven. BLAST analysis of the partial sequences showed that 19 out of the 24 isolates sequenced showed high similarity (> 99%) to those of reference strains of the genera Bacillus and Brevibacillus available in the Genebank and EZ-taxon databases. The five isolates (E5, G2, G8, M1 and M13) that showed moderate similarities (97.2-99%) to strains from the Genebank and EZ-taxon databases were further characterized. Physiological characterization of the five selected isolates based on tolerance to NaCl, temperature and production of hydrolytic enzymes indicated that these isolates are potentially novel. Isolates G8 and M13 showed significantly higher amylase activity (p < 0.05) than the other three isolates. Caseinase activity recorded by the five isolates was the highest (p < 0.05) compared to other enzyme activities. The enzymes produced by thermotolerant bacteria from the five hot springs may be potentially useful for catalysis under harsh operational conditions encountered in industrial processes. Key words: Thermphilic, bacteria, thermozymes, hot springs, Eritrea.
Highlights
The discovery of extremophiles has been a remarkable impetus for biotechnology industries
Thermotolerant bacteria have attracted industrial and biotechnological attention as their enzymes are well suited for harsh industrial processes (Abdel-Rahman et al, 2016; Archna et al, 2015; Verma et al, 2015)
65 thermotolerant bacterial isolates were obtained from the five hot springs in Eritrea
Summary
The discovery of extremophiles has been a remarkable impetus for biotechnology industries. The lack of enzyme stability of mesophilic enzymes renders them inefficient for the harsh reaction conditions required in industrial processes. For this reason, the use of biocatalysts in organic reactions represents only a small fraction of the potential industrial market (Meyer et al, 2012). Thermotolerant bacteria have attracted industrial and biotechnological attention as their enzymes are well suited for harsh industrial processes (Abdel-Rahman et al, 2016; Archna et al, 2015; Verma et al, 2015). Brewing and sugar production require α-amylases that are stable at high temperatures for gelatinization and liquefaction of starch to run processes at a relatively low cost (Rasooli et al, 2008). Only a few of actual applications of these biocatalysts have reached the market (Coker, 2016)
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