Optimization of exopolysaccharide production by pleurotus ostreatus using diffrent cultivation strategies

Abstract

Pleurotus ostreatus or known as oyster mushroom was regarded as one of the most cultivated mushroom around the world. One of the qualities it has is it able to produced exopolysaccharide called pleuran which secreted into the medium during submerged fermentation. The polysaccharide composed mainly of ß-(1/3)-D glucose and ß-(1/6)-D glucose linked by glycosidic bond. It has molecular weight of 2.4 X 104 Da with molecular formula of (C6H10O5)x The importance of pleuran is that it has the immunomodulatory properties that associated in triggering our immune system response. Nowadays, submerged fermentation is considered as the best method in cultivation this kind of mushroom. However, the production process of this kind of mushroom and its exopolysaccharide production especially in term of medium component is still unclear. In this research, the objectives were to optimize the medium composition and to find the optimum carbon to nitrogen (C: N) ratio for high exopolysaccharide production. Eight different media was screened and followed by factor by factor optimization of the medium component. The factors that been studied were ideal concentration of glucose, yeast extract, ammonium sulfate and dipotassium phosphate. Media number six which contain glucose 60.0 g L-1, yeast extract 2.0 g L-1, (NH4)2SO4 5.0 g L-1, MgSO4.7H2O 0.2 g L-1, K2HPO4 1.0 g L-1 was selected as best media production for P. ostreatus cultivation . The experiment then was further with different concentration of each component in the medium six excluding magnesium sulfate heptahydrate which maintained at 0.2 g L-1 throughout all the experiment stage. The range concentration for glucose, yeast extract, ammonium sulfate and dipotassium phosphate was setup between 0 – 120 g L-1, 0 – 4 g L-1, 0 – 5 g L-1 and 0 – 2 g L-1 respectively. In order to get the best C: N ratio for highest exopolysaccharide production, eleven ratio of carbon to nitrogen was experimented ranging from 15:1 to 65:1.Result shown that the optimum concentration for glucose, yeast extract, ammonium sulfate and dipotassium phosphate was 80.0, 4.0, 2.5 and 1.0 g L-1 respectively whiles the optimal C: N ratio recorded was 40: 1. The optimized medium also produced 2.83 g L-1 of exopolysaccharide increasingly up to 49 % when compared with un-optimized medium which only produced 1.9 g L-1 of exopolysaccharide.