High-effective cultivation of Halobacterium salinarum providing with bacteriorhodopsin production under controlled stress

Abstract

Submerged growth of Halobacterium salinarum and therefore synthesis of bacteriorhodopsin (BR) and carotenoids depend greatly on products of both chemical and/or photochemical oxidation of medium components and cellular metabolism which act as inhibitors. Some cultivation variants which allowed eliminating an adverse effect of inhibitors on biomass accumulation and BR synthesis are reviewed. The application of activated charcoal or ion exchange resin as adsorbents at preparing inoculums and the main cultivation stages was shown to allow controlling, namely lowering overstress of the halobacterial cells by metabolites. The halobacterial biomass was accumulated up to 45gL−1 during eight-day cultivation with recycling cell suspension through adsorbent in a fed-batch mode. Such biomass contained up to 1,750mgL−1 BR and a minimum amount of carotenoids; thus the latter contributed to an easier isolation and purification of bacteriorhodopsin. To control BR biosynthesis the express method of BR quantification based on colour shades of cell suspension was developed.