Volume 12 Part 1 Article 34: Bark Wastes for Mushroom Growing

Volume 12 Part 1 Article 34
Year 1989
Title: Bark Wastes for Mushroom Growing
Authors: H.H. Wang, C.T. Sheu and S.L. Lee


Composting is a process of aerobic solid state fermentation (SSF) (Wang 1978) , in which water and oxygen must be available if microbial growth and biochemical activity are to occur. The influence of free-state water on fermantation kinetics in SSF was studied by Narahara et al. (1982) in terms of water activity. Their results suggested that oxygen transfer in this liquid film is an important parameter and is related to the pore spaces among the particulate substrate.

Moisture sorption in solid substrates may be determined by the McConnel and Eastwood method. The substrate is soaked in water at 20°C for 24 hours, then centrifuged at 14.000 g for 1 h. The liquid supernatant is discarded. The moisture content of the pellet is measured and is considered the water holding capacity (WHO. This WHC indicates the maximal water absorption of the substrate, while the moisture at water activity, Aw = 0.9, may indicate a minimum requirement because Aw = 0.9 is generally the lower limit for bacterial growth. The ratio of initial moisture in the substrate to WHC of the substrate determines whether the subsequent fermentation will be aerobic or anaerobic. For example, in the case of mixed hog waste and rice hull as substrates, the ratio of 0.83 indicated anaerobiosis (Cheng, Chiang and Wang 1982). We started a study of the SSF of bark wastes with the adjustment of the initial moisture of the substrates with the reference to moisture sorption curves and water holding capacity (WHC). This kind of approach was described before (Wang 1985, 1987; Wang et al. 1981). The final purpose of the present study is to stabilize the bark wastes for mushroom cultivation by the removal of toxic substrates, and nitrogen immobilization but leaving the lignin in the compost.

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