English abstract
Microbial mats are complex assemblages of different groups of microorganisms that can be found in several extreme environments including hypersaline areas around the world. However, the occurrence and evaluation of hypersaline microbial mats for biotechnological applications in Oman has not been much explored. Hypersaline mats exposed to extreme salinities reaching up to 35% were obtained from Shannah, Oman. Using cultivation methods, a total of 13 bacterial isolates were obtained and identified as species belonging to Bacillus and Halomonas genera using 16S rRNA sequencing. Upon testing for their physiological adaptation to different salinities, temperatures and UV intensities, most of the isolates were halotolerant, mesophilic and UV-resistant. Five out of the 13 isolates identified as Halomonas meridiana and Bacillus haynesii showed not only good antibacterial activity against Pseudomonas aeruginosa, Lysinibacillus tabacifolii, Vibrio gazogenes but also antifungal activity against Fusarium sp. A high content of total antioxidants was detected among many of the isolates. Two strains
belonging to Bacillus subtilis and two belonging to Bacillus vallismortis were found to be capable of secreting high amount of amylase enzyme. Crude amylase enzymes obtained from these strains were found to be alkaliphilic, active at temperature range of 40-60 °C and could tolerate high concentrations of NaCl although inhibited by 10mM of different metallic ions.
Stability of enzyme was high for the first 20 minutes of reaction in all four strains with maximum activity at optimal temperature and pH ranging from 112.96-132.40 U/ml. Application of crude amylases from the two Bacillus subtillis isolates to hydrolyze bread, sweet potato and rice wastes provided an average yield of 9.50 g/L of fermentable sugars from 2.1% raw material
(45% efficiency from total raw material biomass). Using Saccharomyces cerevisiae, the highest amount of bioethanol after two days, amounting to 710.38 (mg/g of sugar) was detected when rice was used as raw material. On the other hand, characterization of the cyanobacteria isolated from our hypersaline mats revealed the presence of a considerable amount of carbohydrates and lipids, highlighting their potential as promising candidates for bioethanol or biodiesel production
in future research. Hence, microbial mats developed from hypersaline regions of Oman present a valuable source of microorganisms that have proved to be of immense potential for several biotechnological applications such as antimicrobial compounds, antioxidants and enzyme production and biofuel generation in future.
