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.
