Extracellular laccase production by bacterial isolates for the treatment of palm oil mill effluents using agro-wastes as a carbon source.

Abstract

Laccase is widely known to oxidize numerous substrates. The laccase-producing isolate used in this study was obtained from a snail gut. Agrowastes were processed using 1 % NaOH and hydrolysed with agrowastes produced by Aspergillus niger. The hydrolysate was used in place of fructose and optimized using Box-Behnken response surface methodology. Submerged fermentation in a Luria Bertani broth supplemented with 0.01 % guaiacol was used to produce laccase based on the optimal conditions. The laccase was partially purified using ammonium sulphate precipitation and used to treat palm oil mill effluents (POME). The laccase-producing isolate was identified as Pseudomonas aeruginosa (accession number OR687603). Corn cob had the highest capacity for laccase production (7.25 U/mL). The optimal production of laccase was achieved at 37 ◦ C, pH 9, 60 h and 3.3 % carbon source. Under these conditions, 60 mL laccase (10.76 U/mL) was produced from a 5 L medium. After treatment there were reductions in chemical oxygen demand (COD) (1875.10–1542.90 mg/L), biochemical oxygen demand (BOD) (23.67 mg/L to 7.33 mg/L) and pH increased from 3.57 to 3.73. The result showed that the laccase produced using corncob as a carbon source can be developed as an environmentally sustainable alternative in POME treatment.