Paper Industry Research And Application Of The Strain And Enzyme

Some fungi were isolated , properties of enzymes produced by these fungi and the stock cultures in our laboratory were analyzed. In which, the fungus W-14 and fungus LZ-8 were selected because of their high abilities to produce cellobiose dehydrogenase (CDH) and laccase respectively. Preliminary experiments showed that the optimum carbon source and nitrogen source for CDH production by fungus W-14 were dewaxed cotton powder and urea respectively. The activity of CDH was 208.4 U/L after 17 days cultivation when fungus W-14 was grown in the medium with the suitable carbon source and nitrogen source.The culture components and fermentation conditions for laccase production in flasks by fungus LZ-8 were investigated in the paper. The results showed that the optimum carbon source was potato and nitrogen source was bean cake powder. The addition of surfactant PEG4000, metal ion Cu²⁺ and Mn²⁺ to basal media enhanced the enzyme production. The suitable culture were as follows: potato 150 g/L, bean cake powder 10 g/L, NaH₂PO₄ 1.5 g/L, K₂HPO₄ 3 g/L, MgSO₄7·H₂O 0.2 g/L, PEG4000 3 g/L, CuSO₄5·H2O 0.0025 g/L, MnSO₄·H₂O 0.05 mg/L, NaCl 0.1 g/L, CaCl₂ 0.01 g/L, veratryl alcohol 1 g/L, and pH 6.0-7.0. The activity of laccase reach 10.86U/ml when fungus LZ-8 was cultured at 30℃ for 9 days with shaking at 150 rpm in the suitable laccase production medium (50 ml in 300 ml conical flask).The properties of laccase produced by fungus LZ-8 were studied. The results showed that the suitable buffer was citric acid-sodium citrate buffer system and the optimum pH and temperature of laccase were pH 4.0 and 40℃ . The enzyme was stable in the range of pH 3.0-9.0 and below 50℃. The activity of laccase was enhanced by Ag⁺ and Zn²⁺, but was strongly inhibited by Fe²⁺ and Fe³⁺.Strains suitable for pulp and paper mill waster water treatment were screened from more than 10 white-rot fungi from the isolated fungi and the stock cultures in our laboratory by cultivating continuously in a series waste water-contained mediums which had increased gradually amount of waster water. Several strains were obtained which were waste water toxicity-resistance and could decrease COD(Chemical oxygen demand) content of waste water effectively. In which, fungus Z-1 and fungus L02 could be used directly for treating middle-stage effluent from pulp and paper mill and led to COD...