Spent ammonium sulphite liquor (SASL) is the main effluent from the ammonium sulphite pulping process, and contains amounts of lignocellulosic oligomers, monosaccharides and ammonium salts. The effect of continuous SASL-feeding on cellulase production by Penicillium oxalicum was studied. With a rate-varying feeding strategy, the maximal filter paper enzyme (FPase) activity reached 17.66U/mL at 144h, and the specific FPase activity increased from 1.74U/mg (without SASL) to 2.40U/mg. Accordingly, the glucan hydrolysis conversion of delignified corn cob residue by the enzymes from continuous SASL-feeding fermentation was significantly higher than that without SASL at equal protein loadings. Comparative proteomic analysis demonstrated that the proteins involved in lignocellulose degradation were specifically up-regulated in the crude cellulase with SASL-feeding. The obtained crude enzyme was efficient in the hydrolysis of pulping products, with a glucan conversion of 81.87% achieved after 72h saccharification of ammonium sulphite pulp.
Keywords: Cellulase; Fed-batch fermentation; Penicillium oxalicum; Spent ammonium sulphite liquor.
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