Bacillus licheniformis proteases as high value added products from fermentation of wastewater sludge: pre-treatment of sludge to increase the performance of the process

Abstract

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.

Ultrasonication of wastewater sludge—Consequences on biodegradability and flowability

“…Additionally, WWS includes, cell wall and the membrane of prokaryotes composed of complex organic materials such as, peptidoglycan, teichoic acids, and complex polysaccharides, which are not readily biodegradable [3]. In this context, several pre-treatment methods such as, thermal and thermo-alkaline hydrolysis and partial oxidation have been effectively applied to enhance biodegradability of WWS with encouraging results in particular for Bacillus thuringiensis biopesticides and Bacillus licheniformis proteases production [4][5][6]. The exposure of insoluble, non-biodegradable (recalcitrant organic matter), and the microbial cells to pre-treatment process rupture the cell wall, and membrane followed by release of the intracellular organics in the bulk solution, which in turn enhances the overall digestibility.…”

Genetic Tools and Techniques for Recombinant Expression in Thermophilic Bacillaceae

“…Furthermore, thermophilic Bacillaceae can be used for constructing DNA libraries useful in identifying genes coding for thermostable proteins as reported by Suzuki et al (2013) and for thermoadaptation-directed evolution of very thermolabile enzymes towards increased thermostability [ 22 , 23 ]. Facultatively thermophilic B. licheniformis is widely used in industry for secretion of native enzymes, e.g., proteases, keratinase, tannase, and others; however, most of the production experiments were performed at mesophilic temperatures [ 4 , 24 , 25 , 26 , 27 , 28 , 29 ].…”

Extracellular polymeric substances production in sludge by bacteria isolated from Hanoi brewery

“…Đây là nguồn nguyên liệu tái sử dụng giá rẻ, giàu cacbon, nitơ và các chất dinh dưỡng khác. Vi sinh vật có thể sử dụng các nguồn dinh dưỡng có sẵn trong bùn thải công nghiệp [4]. Việc tận dụng bùn thải để thay thế cho môi trường nhân tạo đắt tiền trong quá trình nuôi cấy vi sinh vật để tạo ra các sản phẩm sinh học có ý nghĩa lớn vì vừa giúp giảm giá thành vừa góp phần bảo vệ môi trường.…”