OPTIMIZATION OF LACCASE PRODUCTION BY CURVULARIA LUNATA USING MAIZE COB AS SUBSTRATE

A Bello,A I Mohammed-Dabo,D A Machido,S A Ado

doi:10.33003/fjs-2020-0404-503

Abstract

Researchers are showing interest in laccase because it is able to degrade several lignocellulosic biomass. It is important to optimize laccase production to achieve higher yield at a lower cost using agricultural wastes. This study was aimed at optimizing the culture conditions for laccase production. Previously isolated and characterized laccase producing Curvularia lunata was collected from the laboratory of Microbiology department, ABU, Zaria. Maize cobs which were used as substrate were collected from Seed Processing Unit of Institute for Agricultural Research, Zaria and the proximate composition of the substrate was determined according to AOAC guideline. The optimum fermentation type for laccase production was determined after which the culture conditions for laccase production were optimized. Laccase activity was determination by guaiacol assay. The proximate compositions of the maize cob were found to be Moisture content (3.18%), Crude protein (2.50%), Crude fat (32.20%), Crude fibre (3.15), Ash content (1.88%) and Carbohydrate content (57.09%). Higher laccase activity was recorded under solid state fermentation compared to submerged fermentation. The optimum culture conditions were found to be inoculum size 3 x 5 mm, pH 5, incubation temperature 30 oC and incubation period of 6 days. The culture conditions for laccase production by Curvularia lunata using maize cob as substrate were optimized

Highlights

Laccase is an oxidoreductase extracellular enzyme that catalyzes the oxidation of numerous aromatic compounds accompanied by reduction of oxygen to water
Carbohydrate content of the maize cob had the highest composition while ash content had least composition
Curvularia lunata with dark-purple halo on PDA supplemented with 1 mM ABTS presented on Plate 1b indicates laccase production

Summary

Introduction

Laccase is an oxidoreductase extracellular enzyme that catalyzes the oxidation of numerous aromatic compounds accompanied by reduction of oxygen to water. Researchers are paying more attention to laccases due to their ability to oxidize lignin and pollutants that are highly resistant to biodegradation (Hernández-Monjaraz et al, 2018). They are used widely in food, cosmetic, chemical and textile industries as well as in environmental bioremediation (Vantamuri and Kaliwal, 2015). New methods of producing laccases with a higher enzyme activity at a relatively lower cost are required This can be achieved by using lignocellulosic agro-industrial wastes as substrate in the production of laccases (Perdani et al, 2020). The diverse metabolic activity of microbes makes it possible for them to use various chemicals (toxic and non-toxic) as source of carbon, nitrogen, phosphorus etc. and after utilization, most toxic chemicals become completely non-toxic (Sinha et al, 2009; Sondhi and Saini, 2019; Thakkar et al, 2020)

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