미세조류 발효산물로서 휘발성 지방산을 활용한 효모의 배양 및 지질축적에 관한 연구

Abstract

This study suggested application of microalgae fermentation effluent as substrate for yeast cultivation. Most of carbon sources in the effluent were volatile fatty acids (VFAs), especially acetic acid. Cryptococcus curvatus, which is one of the well-known oleaginous yeasts obtained significant specific growth rate when grown on acetic acid as sole carbon source. Various microalgae biomass (lipid-extracted microalgae with different biomass loading, differently pre-treated algal bloom) were fermented to produce VFAs. Then the effluent was used as medium for yeast cultivation. Lipid content was the highest (65.71%, g/g) when using 10 g/L lipid-extracted microalgae as biomass for VFAs production. However, in terms of lipid productivity, it was the highest (0.28, g/L/d) when using 40 g/L lipid-extracted microalgae fermentation effluent as cultivation medium, with lipid content of 33.68%. Two-stage sequential batch cultivation system was applied to enhance the lipid content, with nitrogen-deficient condition in the 2nd stage. After 4 times of sequential batch cultivation, the lipid content was increased from 32.01% to 69.09% when grown on VFAs medium from lipid-extracted microalgae. According to fatty acid methyl esters (FAMEs) analysis, the lipid consisted of mostly C16 - C18 fatty acids (98.49%). The fatty acid profile of microbial lipid was similar with that of plant oil, mostly oleic acid (55.20%), linoleic acid (16.46%), stearic acid (13.12%) and palmitic acid (12.99%), which qualified appropriate fatty acids composition for biodiesel performance. From the result, the lipid extracted from C. curvatus cultivated on VFAs medium produced from microalgae fermentation possessed suitable quality as biodiesel.