Roles of water in improved production of mycelial biomass and lignocellulose-degrading enzymes by water-supply solid-state fermentation of Ganoderma lucidum

Abstract

The liquid phase was proved to be a significant influencing factor among the three phases in solid-state fermentation (SSF), which determined water control was crucial. However, obvious water loss was caused by microbial utilization and moisture evaporation. Super absorbent polymer (SAP) was utilized to supply water in SSF owing to its high water-holding capacity. Adding 0.15% SAP could significantly increase the biomass of Ganoderma lucidum by 33.59% and promote filter paper activity (FPA), endocellulase activity and laccase activity by 27.11%, 29.14% and 47.39%, respectively. Water states of fermentation substrates were detected by the low-field nuclear magnetic resonance (LF-NMR). Results revealed that water present and lost was dominated by the capillary water. At the end of fermentation, the capillary water content (Ccw) in water-supply SSF was 20.48% and 17.20% higher than that in static SSF and cold-model SSF. The relaxation time of the capillary water was reduced by 56.53% in water-supply SSF and by 53.40% in static SSF, but it just reduced by 6.82% in cold-model SSF. In addition, the Ccw in SSF had a high correlation with the biomass and lignocellulose-degrading enzyme activities of G.lucidum. These results clearly demonstrated that capillary water played a very important role in improved production of G.lucidum.