Abstract
Cassava (Manihot esculenta, Crantz) is one of the most important food plants in West Africa. Its peels are made up of cellulose, hemicellulose and lignin. This lignocellulolytic biomass can be converted using microbial enzymes to fermentable sugars which have wide range of biotechnological relevance in many fermentation processes. The aim of this study is to screen filamentous fungi from decaying cassava peels that are good producers of xylanases and cellulases. Decaying parts of cassava peels were obtained and brought to the laboratory for further work. Fungi were isolated, identified and screened for cellulase and xylanase production. Isolate with highest frequency of occurrence and enzyme production was identified using phenotypic and molecular method. Optimisation of growth conditions for enzymes production was monitored using the DNSA method, also saccharification of cassava peel were carried out using the enzymes obtained from the isolate. Aspergillus terreus KJ829487 was the predominant fungus. It produces cellulases and xylanases optimally at 40°C, pH 6 and 8, utilising carboxymethylcellulose (CMC) or xylose and yeast extracts as its carbon and nitrogen sources respectively. Saccharification of the peels yielded 584 mg/L glucose, 78 mg/L xylose and 66 mg/L rhamnose. Aspergillus terreus KJ829487 obtained from cassava peels have the ability to produce high concentration cellulases and xylanases which effectively hydrolysed the lignocelluloses’ biomass to fermentable sugars.
Highlights
Cassava (Manihot esculenta, Crantz) peels are the main by-product from processing tuberous roots of cassava for human consumption
Cassava peels are lignocellulolytic biomass which is considered as an agricultural residue because it is discarded during processing
The genera Trichoderma, Aspergillus, Penicillium, Humicola are described as cellulase producers, Aspergillus spp. is the major agents of decomposition and decay, they produce a broad range of enzymes, including cellulases and xylanases and these reports have been well documented [3]-[8]
Summary
Cassava (Manihot esculenta, Crantz) peels are the main by-product from processing tuberous roots of cassava for human consumption. Cassava peels are lignocellulolytic biomass which is considered as an agricultural residue because it is discarded during processing. The degradation of this complex structure requires a complete enzymatic system. Efficient hydrolysis of cellulose requires the action of a complex of cellulolytic enzymes that work synergistically: exo-1, 4-β-D-glucanases, endo-1-4-β-D-glucanases and 1,4-β-Dglucanases [2]. The production of cellulases by fungi and bacteria is widely disseminated in nature. There is an increasing demand for these enzymes, especially for bioconversion of agricultural resources and ethanol production because cellulase helps in hydrolyzing cellulose to produce glucose [9]
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