Significance of inoculation density and carbon source on the mycelial growth and Tuber polysaccharides production by submerged fermentation of Chinese truffle Tuber sinense

Abstract

Truffles are among the most valuable gourmet mushrooms on the market. By taking Chinese truffle Tuber sinense as a typical example, a submerged fermentation process for the production of mycelia and Tuber polysaccharides was developed for the first time. Significances of inoculation density, carbon source and its initial concentration were studied in details. For inoculation density within the range of 160–653 mg dry weight (DW)/L, a maximal biomass of 15.59 ± 0.59 g DW/L was obtained at its lowest level of 160 mg DW/L, while the maximal extracellular polysaccharides (EPSs) production of 1.97 ± 0.08 g/L was attained at its highest level of 653 mg DW/L. The maximal intracellular polysaccharides (IPSs) production of 1.40 ± 0.10 g/L was obtained at its level of 487 mg DW/L. The carbon sources examined were glucose, maltose, sucrose and lactose, and sucrose was suitable for the cell growth and IPS production. Lactose was beneficial for EPS production although the cell could not grow well. There was no β-galactosidase activity when T. sinense grew in lactose, which was the reason why lactose was not favorable for the cell growth. Initial sucrose concentration within the range of 20–125 g/L significantly affected the process. At sucrose 125 g/L, both biomass (i.e., 24.07 ± 1.94 g/L) and EPS production (i.e., 2.85 ± 0.04 g/L) reached their peak values. The maximal IPS production of 2.92 ± 0.20 g/L was obtained at sucrose 80 g/L. This work demonstrated the submerged fermentation of Chinese truffle T. sinense is a potential alternative for the efficient production of mycelia and Tuber polysaccharides.