Study on the effect of medium composition and culture conditions on biomass and lipid production of Physarum polycephalum microplasmodia

Abstract

Physarum polycephalum is a species of myxomycetes or slime molds (fungus – like protozoans.). Microplasmodia of this organism lack cell walls and are capable of fastgrowing under simple culture conditions. Lipids extracted from this species were reported to have great potential for dietary supplements and functional food applications. Thus, the main purpose of this study was to optimize fresh sugarcane juice-based culture medium composition for P. polycephalum microplasmodia biomass and lipid production. Optimization of sugar cane-based medium components by Response Surface Methodology (RSM) showed that sugarcane concentration had significant influences on biomass production (p-value: 0.0093). The optimal medium comprised of 333 ml fresh sugarcane juice (equivalent to 40 g/L of reducing sugars), 10 g/L tryptone and 4 g/L yeast extract. This medium yielded 14.588 g/L dry cell weight and 2.111g/L of lipid after five days. These figures were higher than the amount of biomass (13.86 g/L) and lipid (1.97 g/L) obtained from P. polycephalum microplasmodia cultured in the optimal glucose-based medium. Lipid composition analysis by GC-MS showed that the microplasmodia lipid of the biomass in sugarcane juice-based culture was composed mainly of linoleic acid (48.353%), oleic acid (35.712%), and palmitic acid (7.232%). These percentages of linoleic acid and oleic acid were significantly higher, whereas oleic acid content was lower than those of the biomass in glucose-based culture, of which those contents were 10.050%, 40.460%, respectively. Having high amounts of unsaturated fatty acids suggested that P. polycephalum could be a promising source of biomass for dietary supplements and functional food.