Department of Nutrition and Food Science

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Browsing Department of Nutrition and Food Science by Subject "Fermentable Sugars"

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    Optimisation of the Parameters for Bio-Processing of Cassava Peel to Increase Fermentable Sugars and Lysine Production
    (University of Ghana, 2017-07) Bayitse, R.
    Bio-processing of cassava peel for Lysine production was done by characterising the cassava peel for carbohydrate types. The process of enzymatic hydrolysis of the cassava peel was optimised to produce fermentable sugars using response surface methodology. The hydrolysed cassava peel was used as a source of carbon to optimise the conditions for lysine production using mutant Corynebacterium glutamicum (AHP3) strain. Cassava peel is a biomass generated as a result of processing cassava tuber by peeling operations. It is a natural resource that shows heterogeneity in structure and chemical composition. Physical and chemical composition analysis was done using standard methods. It was found that nearly 83 % dry matter (DM) composition of the cassava peel was glucose whiles xylose and arabinose have made up only small amount of 2.31 and 2.35 % respectively. The cellulose and hemicellulose were 6.0 % DM and 2.23 % DM respectively and the residual starch content was 47.16 %. The protein was 2.40 % and the cyanide level was 9.3 mg/kg. The lignin and the ash contents were 1.92% and 6.30% respectively. The high level of residual starch and low amount of lignin make the cassava peel very susceptible to enzymatic hydrolysis without laborious pretreatment regimes. Importantly, this study provides a useful base line data for agro-economic evaluation of cassava peel as a feedstock for an integrated biorefinery, because the valorisation of cassava peel is still overlooked and not fully exploited. Additionally, deep understandings of the biomass chemical and physical characteristics need to be known in order to assist in designing safe processing facilities. Cassava peel is normally considered as waste because of its limited use. Composition analysis revealed that it contained appreciable amount of starch which can be hydrolysed to fermentable sugars. Response Surface Methodology using Central Composite Design (CCD) was applied to optimise the enzymatic hydrolysis of cassava peel in order to produce glucose. Two effective approaches were used in the study. The first one was to optimise the enzymatic hydrolysis process using cellulase, β-glucosidase, amyloglucosidase and α-amylase. The second approach was to optimise enzymatic hydrolysis using the mixture of these enzymes. The effects of enzyme loading, hydrolysis time, substrate concentration, pH and temperature on glucose recovery were investigated. The results were subjected to analysis of variance (ANOVA) to produce polynomial regression model. Mean interaction plot and their effect on glucose recovery were drawn to determine the optimal conditions for enzymatic process. Targeted hydrolysis of specific carbohydrate types in cassava peels with single enzymes showed optimised levels of glucose recovery of over 80% for starch hydrolysing enzymes and about 5% for cellulose hydrolysing enzymes at 0.06 g/ml substrate water ratio at 24 hours of hydrolysis. Single step hydrolysis of cassava peel with mixed enzymes of starch and cellulose hydrolysis enzymes at optimised conditions of celulase (30 FPU/g), β- glucosidase (1.25 U/g), amyloglucosidase (30 U/g), α-amylase (30 U/g), pH 4 and 50 ᵒC at 24 hours produced recovered glucose of about 100%. The present study revealed that lysine biosynthesis from Corynebacterium glutamicum can be significantly enhanced by optimising the fermentation process. Different ingredients have an essential role in the metabolic pathway of the organism for lysine production. Carbon and nitrogen sources from cassava peel hydrolysate have also been found to have influential role in the amino acid production. Central Composite Design (CCD) was applied to optimise the amino acid fermentation process in order to produce lysine. The effects of substrate concentration, microbial load and time of fermentation on growth of C glutamicum, glucose utilisation and lysine production were investigated. The results were subjected to analysis of variance (ANOVA) to produce polynomial regression model. Mean interaction plot and their effect on microbial growth, glucose consumption and lysine production were drawn to determine the optimal conditions for amino acid fermentation process for lysine production. Glucose utilisation reduced at higher hydrolysate concentration thereby affecting microbial growth. Lysine production was optimum at low initial microbial load of 0.05 nm (OD) and cassava peel hydrolysate concentration not more than 35% (v/v) at 48 hours fermentation.