Scale up studies on select bacterial strains for improvement of PUFA production

Abstract

The sustainable production of polyunsaturated fatty acids (PUFAs) from microorganisms has been a focus for several decades. A rising demand for healthy superfoods like PUFA and a decline in their natural sources have prompted the development of faster, more reliable, and more economical microbial production strategies. Unlike algae and fungi, bacteria pose a clear advantage w.r.t. ease of culturing, manipulation, and production speeds. In the present study, two bacterial cultures isolated from the Arabian Sea and one river water Bacillus species were studied for their PUFA-producing capability at the lab-scale bioreactor level. These isolates, previously studied for their maximum PUFA output at the shake flask level, were put under lab-scale bioreactor conditions in an attempt to increase productivity. This investigation was carried out using fed-batch and single-batch culture techniques, with regulated environmental parameters, improved aeration, mixing, and a set C: N ratio. With careful monitoring, up to 20% PUFA and 7.9 g/L dry biomass could be obtained from saltwater Halomonas spp. While the freshwater Bacillus thuringiensis spp. reached a maximum of 11.79% PUFA and 5.6 g/L of dry biomass. The fed-batch mode proved to be more effective, increasing biomass and PUFA production by three to fivefold. Compared to earlier research using the same bacterial isolates in shake flask cultures, the results achieved were significantly higher. Elementary fermentation process data obtained through this investigation will be valuable in promoting further scale-up studies for bacterial PUFA production.