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VOL. 6, ISSUE 4 (2021)
Optimization of process condition for laboratory scale enzymatic conversion of cassava starch to glucose syrup
Authors
Henry O Chibudike, Nelly A Ndukwe, Adekunle K Lawal, Eunice C Chibudike, Olubamike A Adeyoju
Abstract
Enzymatic hydrolysis of cassava starch for producing glucose syrup was evaluated using alpha-amylase (Novo’s Termamyl 120L) and glucoamylase (Novo’s AMG 300L). The cassava roots were detoxified, sliced and blended with deionized water forming a suspension of 35% (w/v) of the extracted cassava bringing the total weight of slurry to 120 g. The slurry was adjusted to different pH ranging from 5 to 8 (i.e. 5, 6, 7, 8) by the addition of varying drops of 1 N NaOH. The suspension was maintained under heating, increasing the temperature in 1 °C/minute, until the starch was completely dissolved. Calcium was added using calcium hydroxide (Calcium ions stabilizes the enzyme). After, it was cooled down, following stirring of the slurry for approximately 3 min, the slurry was subjected to enzymatic liquefaction carried out by addition of varying doses of 3.5ml, 7.0ml, 10.5ml and 14ml thermostable α-amylase per 120g of cassava slurry (venzyme/wfresh mash) and instantaneously heated to 100 oC and held at this temperature for 10 min before it is cooled to 90 oC and incubated in a water bath at this temperature for 2 hours to further hydrolyze the starch for total liquefaction and production of maltodextrin with a dextrose equivalent (DE) between 12 and 15. The resultant maltodextrin was further subjected to saccharification process in order to obtain a glucose syrup (GS) after adjusting its pH to varying levels (4.2, 4.4, 4.6, 4.8) for each saccharification experiment by adding varying proportions of 0.2 M of acetate buffer and the solution was cooled to 60 oC. Varying concentration of previously produced and characterized glucoamylase solution (25, 50, 75, and 100ml) was added respectively and incubated at 60°C) for 48 hours under constant agitation. The glucose production was monitored using the glucose oxidase method. DE was achieved in varying degrees that ranged from 12.1±4.9 to 73.9±7.6. After this process, the resulting syrup was purified by ion exchanged chromatography using Amberlite Ira 120 (Cationic resin) and Amberlite Ira 410 (Anionic resin) and then concentrated by evaporation under reduced pressure. All experiments were carried out in duplicate and analysis of variance (ANOVA) using central composite experimental design with comparison test at p≤0.05 was used to measure the effect of changing variables among treatments. Correlation Pearson’s test were applied to measure the strength of the interactions between the variables. Enzyme conditions for starch hydrolysis were optimized by a factorial experimental design (4x4x4=64) using various values of pH, reaction time and enzyme concentration. Analysis show that enzymes used in this investigation possess some remarkable properties which include quantitative conversion of starch to glucose. The starch extracted from cassava after complete liquefaction by alpha-amylase produced high starch conversion to maltodextrin syrup furnishing 105.2±1.3ml at enzyme concentration of 14ml, pH value of 7 and liquefaction time of 2 hours. Liquid glucose produced with the pure glucoamylase from Aspergillus niger revealed a dextrose equivalent of 73.9±7.6 at pH value of 4.6 and 150ml enzyme/105.2±1.3ml Maltodextrin at the end of the saccharification process. Cassava starch exhibited good potential as substrates for glucose syrup production.
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Pages:51-58
How to cite this article:
Henry O Chibudike, Nelly A Ndukwe, Adekunle K Lawal, Eunice C Chibudike, Olubamike A Adeyoju "Optimization of process condition for laboratory scale enzymatic conversion of cassava starch to glucose syrup ". International Journal of Food Science and Nutrition, Vol 6, Issue 4, 2021, Pages 51-58
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