Abstract:

In an attempt to optimize the culture medium for fibre degradation of brewers’grains by Neurospora crass, Plackett-Burman design and central composite design combined with response surface methodology were employed in this work. First, the effects of soybean residues, (NH4)2SO4, urea, KH2PO4, CaCl2 and MgSO4 on fibre degradation by Neurospora crassa were evaluated by a Plackett-Burman design leading to 8 experiments and the most important affecting factors were screened. Subsequently, the interactive effects of the screened factors on fibre degradation were determined using response surface methodology based on a five-variable, five-level central composite design involving 32 experiments. Results indicated that CaCl2, KH2PO4, soybean residues, (NH4)2SO4 and MgSO4 were among the most important affecting factors of fibre degradation. The optimal culture medium consisted of 26.08% soybean residues, 3.71% (NH4)2SO4, 1.53% KH2PO4, 0.24% CaCl2 and 0.08% MgSO4. Three replicate fermentations using the optimized culture medium all gave a value of fibre degradation rate which was in good agreement with the predicted value.

Key words: Neurospora crassa, Plackett-Burman design, response surface methodology, brewers’grains, culture medium