Abstract
The objective of this work was to increase laccase production by Pleurotus ostreatus PLAB through culture medium optimization using solid state culture conditions. Increased laccase activity was obtained through design of experiments (DOE) using the Taguchi orthogonal array (OA). Seven factors, viz. lignocellulose, glucose, yeast extract, peptone, KH(2)PO(4), MgSO(4) 7H(2)O and MnSO(4) H(2)O at three levels and pH at two levels. OA layout of L18 (2(1) x 3(7)) was selected for the proposed experimental design using Minitab 17 software. Data analysis showed that lignocellulose (20 %) and glucose (10 g L1) had positive effect, whereas KH(2)PO(4), MgSO(4)∙7H(2)O and MnSO(4)∙H(2)O did not have significant effect on laccase production. Taguchi OA analysis showed that pH 6, lignocellulose 20 %, glucose 10 g L(-1), yeast extract 6 g L(-1), peptone 15 g L(-1), KH(2)PO(4) 3 g L1, MgSO(4)∙7H(2)O 0.5 g L(-1) and MnSO(4)∙H(2)O 0.1 g L-1 were the optimal conditions to maximize laccase production. The model predicted a 30.37 U g(-1) dry wt., which agreed with the experimentally obtained laccase activity 29.15 U g(-1) dry wt. at optimal conditions.
Highlights
A preliminary study was conducted for studying the ability of production exo-glucanase, endo-glucanase, β-glucosidase, xylanase and laccase of white rot basidiomycete P. ostreatus PLAB
P. ostreatus was inoculated on wheat bran (WB) and beech sawdust substrates, which were mixed in different ratios with lignocellulose biomass (LB)
The results indicated low activity for cellulytic enzymes and xylanase for all six investigated substrates while the laccase activities reached the highest value (17.35 U g–1 dry wt) in comparison to other enzymes
Summary
Laccases (EC 1.10.3.2; benzenediol: oxygen oxidoreductase) are blue multi-copper oxidases with ability to catalyse the oxidation of a wide variety of organic compounds such as mono-, di- and polyphenols, aminophenols, methoxyphenols, aromatic amines and ascorbic acid.[1,2] Beside their biotechnological potential in diverse fields of industrial applications related to bioremediation; including delignification of lignocellulosic, colour removal and detoxification of industrial dyes, bioremediation of xenobiotic compounds, pesticides, explosives, wastewater treatment, and treatment of other pollutants such as polycyclic aromatic hydrocarbons (PAHs).[2,3] Efficient laccase production requires combinations of several factors, such as an easy to grow fungal strain with the ability to secrete specific enzymes, appropriate culture media, an addition of inducers and appropriately selected cultivation system. The influence of single factor on the laccase production has been studied, but mostly different parameters in production media composition have been optimized.[4,5,6,7,8,9] It is known that fungal laccases production, that of white – rot basidiomycetes, can be affected by type and concentration of carbon and nitrogen source and by the presence of copper and organic compounds which function as inducers of laccase activity.[10,11,12,13].
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