Selection of Schizochytrium limacinum mutants based on butanol tolerance

Background: Mutation breeding is one of the most important routes to achieving high docosahexaenoic acid (DHA) productivity using Schizochytrium. However, few selection strategies have been reported that aim to generate a high DHA content in Schizochytrium lipids. Results: First, culture temperature altered the butanol tolerance of Schizochytrium limacinum B4D1. Second, S. limacinum E8 was obtained by selecting mutants with high butanol tolerance. This mutant exhibited a 17.97% lower proportion of DHA than the parent strain S. limacinum B4D1. Third, a negative selection strategy was designed in which S. limacinum F6, a mutant with poor butanol tolerance, was obtained. The proportion of DHA in S. limacinum F6 was 11.22% higher than that of parent strain S. limacinum B4D1. Finally, the performances of S. limacinum B4D1, E8 and F6 were compared. These three strains had different fatty acid profiles, but there was no statistical difference in their biomasses and lipid yields. Conclusion: It was feasible to identified the relative DHA content of S. limacinum mutants based on their butanol tolerance.

Optimization of lipid enriched biomass production from oleaginous fungus using response surface methodology.

Oleaginous microorganisms have emerged as potential sources of oils for biodiesel production. To replenish as an alternative to the vegetable oils, higher lipid accumulating strain coupled with process optimization is indispensable. In the present study, response surface methodology (RSM) based central composite design (CCD) was used for optimization of lipid content from oleaginous fungus Aspergillus sp. Maximum lipid yield of 73.07% (w/w) was achieved at 3% (v/v) inoculum volume, pH 5, glucose 1% (w/v), urea 0.5 % (w/v) and incubation time of 5 (days). Biomass (2.08 g/L) having a lipid content of 73.07 % (w/w) with major constituents of hexadecanoic acid methyl ester and 9-Octadecenoic acid methyl ester were obtained. The lipid composition signifies that from the oleaginous microbe are highly encouraging and desirable to be considered as diesel substitute.