Wastewater sludge is a complex raw material that can support growth and protease production by Bacillus licheniformis. In this study, sludge was treated by different thermo-alkaline pre-treatment methods and subjected to Bacillus licheniformis fermentation in bench scale fermentors under controlled conditions. Thermo-alkaline treatment was found to be an effective pre-treatment process in order to enhance the proteolytic activity. Among the different pre-treated sludges tested, a mixture of raw and hydrolysed sludge caused an increase of 15% in the protease activity, as compared to the untreated sludge. The benefit of hydrolysis has been attributed to a better oxygen transfer due to decrease in media viscosity and to an increase in nutrient availability. Foam formation was a major concern during fermentation with hydrolysed sludge. The studies showed that addition of a chemical anti-foaming agent (polypropylene glycol) during fermentation to control foam could negatively influence the protease production by increasing the viscosity of sludge.
Bacillus licheniformis proteases as high value added products from fermentation of wastewater sludge: pre-treatment of sludge to increase the performance of the process
M. Drouin, C. K. Lai, R. D. Tyagi, R. Y. Surampalli; Bacillus licheniformis proteases as high value added products from fermentation of wastewater sludge: pre-treatment of sludge to increase the performance of the process. Water Sci Technol 1 February 2008; 57 (3): 423–429. doi: https://doi.org/10.2166/wst.2008.007
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