Optimization of conditions for pectinase production by Saccharomyces cerevisiae ATTC 52712 in solid state fermentation (SSF) and evaluation of its efficacy in orange juice extraction

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APRIL, 2016
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Pectinases are the group of enzymes which degrade pectin and are one of the most used enzymes in food industry. In fruit juice industry, pectinases are often used to enhance juice extraction. This study sought to optimize conditions for pectinase production from Saccharomyces cerevisiae ATCC 52712 and evaluate its efficacy in orange juice extraction. The study was undertaken in two phases, that is, optimization of conditions during fermentation for the enzyme production and its extraction from the solid medium, and assessing the efficacy of the enzyme produced in juice extraction. The optimal conditions investigated in first stage were fermentation time, proportion of corn cobs and orange peels, pH, temperature and inoculum size during the fermentation period for enzyme production, agitation time during enzyme extraction and the best extraction solvent for enzyme recovery. In the second stage, the crude enzyme was concentrated by ammonium sulphate precipitation and used to study the best reaction time and enzyme dosage required for optimal juice extraction. The optimal conditions obtained in the first stage were 6 days of fermentation, 80:20 % for corn cobs to orange peels, pH of 4 at 30 oC, 10.46 x 106 cells/ml, 30 minutes agitation during enzyme extraction and 0.1 M NaCl as best extraction solvent. The optimal conditions obtained with respect to assessment of the efficacy of the enzyme produced with 60 % (NH4)2SO4 saturation of the crude enzyme solution resulted in 45 minutes reaction/holding time and an enzyme dosage of 40 mg total protein per 200 g of orange mash (0.02 %). Significant increase (p<0.05) in activity was obtained when the crude enzyme produced was saturated to 60 % (NH4)2SO4 concentration. During juice extraction, an enzyme dosage of 10 mg total protein per 200 g of orange mash resulted in 15 % increase in free-run juice while 40 mg total protein per 200 g of orange mash enzyme dosage gave an increase of 123.4 % juice extracted over control. This study showed that the activity of pectolytic enzymes from S. cerevisiae produced under optimal conditions enhanced orange juice extraction significantly thereby making the technology useful in improving orange juice production.
Thesis submitted to the Department of Biochemistry and Biotechnology, College of Science in partial fulfilment of the requirements for the degree of Master of Science in Biotechnology.