Bacteriorhodopsin Producing Halophilic Archaea Isolated from Solar Salt Pan Saline Environment for Conversion of Light Energy into Electrical Energy
Abstract
Haloarchaea inhabiting hypersaline environments like solar salt pan ecosystem require at least 1.5 M NaCl for their growth, while their optimum growth is observed at 3.5-4.5 M NaCl. A Few haloarchaeal genera possess a unique retinal protein, bacteriorhodopsin (BR) in their cell membrane which is a photochemical material that acts as a light driven proton pump and converts light energy into electrochemical energy in form of Adenosine Tri Phosphate (ATP) and proton gradient to generate electric potential. In the present investigation, haloarchaea isolated from Shiroda solar salt pan ecosystem situated in District Sindhudurga, West Coast of Maharashtra, India, were explored for production of BR and its direct application in conversion of light energy into electrical energy. The haloarchaeal strain, Sh2.2 from crude salt of salt pan ecosystem was identified as Halovivax asiaticus and found to produce 161 mg/l of BR. It’s capability of converting light energy into electric potential (34.6 mV) appears to be the first report. The strains Sh3.1, Sh3.2 and Sh5.2 isolated from brine sample and wet soil in the vicinity of salt pan and identified as Halorubrum sodomense were found to produce BR in the range of 26-191 mg/l, which is much higher than the earlier reported one i.e. 12.3 mg/l.