Water supply from various sources has different effects on solid-state fermentation of Ganoderma lucidum.

Water is essential in solid-state fermentation (SSF), but the impact of different water sources on SSF efficiency remains unclear. This study investigated the effects of different water sources on water-supply SSF of Ganoderma lucidum. The results showed that supplementation with normal saline led to the highest levels of laccase, CMCase, FPA activities, and biomass of G. lucidum (93.47, 140.34, 172.42 U/g, and 0.19 g/g, respectively), almost all significantly higher than those in the tap water group (83.57, 126.36, 167.17 U/g, and 0.18 g/g) and the deionized water group (77.25, 120.91, 145.50 U/g, and 0.16 g/g). Normal saline also significantly increased the capillary water content during SSF, which was 5.38% and 19.05% higher than that in the tap water and deionized water groups, respectively. Furthermore, the relaxation time of capillary water in the normal saline group decreased by 49.09%, a reduction that was higher than those observed in the tap water group (43.41%) and the deionized water group (29.56%). In conclusion, normal saline demonstrated distinct advantages in enhancing SSF efficiency, thus providing a scientific basis for the selection of water sources in the fermentation of G. lucidum and other microorganisms.