Title
Screening of Cordyceps strains and optimization of its solid-state fermentation conditions on bioconversion of Astragalus residues
Authors
ZHEN-YUAN ZHU YANG LI HUI-QING SUN LI-JING CHENYA-LI TANG XIAO-CUI LIU and YONG-MIN ZHANG

Received February 25, 2014
Published Volume 50 Issue 2 February
Keywords Astragalus residue,·Cordyceps Paecilomyces sinensis,·solid-state fermentation

Abstract
The Astragalus residue is produced after the extraction of Astragalus polysaccharides (APS). In Astragalus residue, the main ingredient is crude fiber. The crude fiber is considered to be the main source for green chemicals, bio-fuels and bio-based products. In this study, we used five kinds of Cordyceps as fermentation strains and Astragalus residue as fermentation substrate for solid-state fermentation. Crude fiber degradation rate after fermentation was considered as the main indicator. The mannitol content and soluble sugar content of the fermentation product were used as secondary indicators. The experiments were carried out by screening the solid-state fermentation strains, optimizing the solid-state fermentation conditions and studying the pilot-scale cultivation of solid-state fermentation. From the results of screening the solid-state fermentation strains, we selected the Paecilomyces bainier strain for further investigation. The fermentation conditions were optimized with four single factors, including fermentation time, solid fermentation inoculum size, pH value of solid medium and fermentation substrate thickness. The single-factor tests revealed that the optimum conditions were the following: fermentation time of 25 days, fermentation substrate pH of the initial value, inoculum of 20% and fermentation substrate thickness of 1.0 cm.