Lipid production from Zygosaccharomyces siamensis AP1 using sequencing batch method with acetic acid as carbon source

Abstract

Microbial lipid made by microorganisms is a promising feedstock to produce biodiesel. One important parameter in the production of microbial lipids is carbon sources. Low-cost carbon sources are one of the considerations for large-scale microbial lipid production. Acetic acid is a low-cost carbon source and can increase the rate of lipid accumulation due to its shorter metabolic pathway. This research aims to evaluate sequencing batch method to increase the lipid production of Zygosaccharomyces siamensis AP1 using carbon sources of acetic acid. The optimum acetic acid for lipid production was first determined by growing the strain in Nitrogen Limited Medium (NLM) with varying concentrations of acetic acid (5 to 40 g/L). Effect of pre-culturing was determined next by growing the yeast in Nitrogen Rich Medium (NRM) with varied acetic acid concentration (5-40 g/L) before lipid production in optimised NLM. Lastly, sequencing batch cultivation was carried out using the optimised pre-culture medium (NRM) and the production medium (NLM). The result shows that Z. siamensis AP1 obtained its highest lipid production when the yeast was grown with 40 g / L of acetic acid. Total lipid increased by 64 % when yeast was pre-culture in NRM containing 40 g/L acetic acid. Sequencing batch method resulted in biomass and total lipid of 0.61 g/L and 0.48 g/L, respectively. Half of the lipid was produced extracellularly. This study suggests that acetic acid can be used as a single carbon source in lipid production from Z. siamensis AP1. It also shows that sequencing batch method with pre-culturing can increase the lipid production. Besides, the method triggers excretion of the produced lipid out of the yeast cells. Further study to investigate the role of acetic acid in Z. siamensis AP1 extracellular lipid production is suggested.