Optimization of submerged culture for exopolysaccharides production by Morcella esculenta and its antioxidant activities in vitro

Abstract

Morcella esculenta is an excellently edible and delicious morel mushroom found growing in China, Japan, and other Asian countries. Polysaccharides extracted from fungi have shown a variety of medical activities; however, the industrial large-scale production of Morcella esculenta can not be achieved now due to the natural conditions. So this paper is concerned with optimization of submerged culture conditions for mycelial growth and exopolysaccharides (EPS) production of Morcella esculenta. by airlift fermentation. And the antioxidant activities of EPS were revealed by various free radical scavenging assays in vitro. The optimal medium constituents were determined as follows: (g/L): glucose 20 g/L, peptone 4.5 g/L, KH2PO4 0.8 g/L, and MgSO4·7H2O 1.0 g/L. The optimum parameters of liquid culture were temperature 25 °C, cultivation time 5 d, rotary speed 140 rpm, and initial pH 6.0. This optimization strategy in shake flask culture leads to a mycelia yield of 4.93 ± 0.28 g/L, and EPS production of 1.65 ± 0.28 g/L, respectively. Under optimal culture conditions, the maximum mycelia and EPS concentration in a 7 L airlift tower loop reactor were 6.13 g/L and 2.12 g/L for the first report, which were considerably higher than those obtained in preliminary studies that indicated the EPS production was closely correlated to the mycelia growth by Morcella esculenta. Futuremore, the EPS demonstrated positively antioxidant potential on 1,1-diphenyl-2-picrylhydrazyl radical scavenging, reducing power, and hydroxyl radical scavenging. These findings may provide the basis for the popular use of EPS in functional food or medicine. © Springer-Verlag Berlin Heidelberg 2014.