Bioconversion of waste sheep wool to microbial peptone by Bacillus licheniformisEY2

Abstract

Peptones are among the most expensive culture components used in the cultivation of microorganisms. This study was performed to prepare a protein hydrolysate from sheep wool using a locally isolated keratinolytic bacterium Bacillus licheniformis EY2 (GenBank: MN809476), and to investigate the usability of the prepared hydrolysate as a peptone in a microbial medium. The optimum pH, temperature, and incubation time for wool hydrolysis and keratinolytic activity were determined as 7.0, 55 °C, and 6 days, respectively. Optimum concentrations of KH2PO4, MgSO4, and NaCl were determined as 1.5, 0.5, and 2 g/L, respectively. After the prepared hydrolysate was partially purified, it was converted to wool peptone (WP). The total protein, ash, carbohydrate, and lipid content of WP was found to be 82.7, 7.2, 0.1, and 0.2 g/100 g, respectively. Fourier transform infrared (FTIR) analysis of WP confirmed the formation of sulfoxide bonds (S=O), which indicated the breaking of disulfide bonds. When compared with commercial tryptone peptone (TP), WP was found to be superior for the cell growth performances of Esherichia coli, Bacillus subtilis, Staphylococcus aureus, Lactobacillus plantarum, Pediococcus pentosaceus, Candia albicans and Aspergillus niger. A protein hydrolysate (including wool protein hydrolysate) prepared via microbial hydrolysis was tested for the first time as a peptone source. The cost of WP is much lower than commercial peptones. At the same time, the method developed offers an environmentally friendly approach for the reduction of the amount of unutilized or waste sheep wool. © 2021 Society of Industrial Chemistry and John Wiley & Sons Ltd.

Wool keratin as a novel alternative protein: A comprehensive review of extraction, purification, nutrition, safety, and food applications

“…Purified enzymes are expensive, prompting the direct use of microbes on the substrate as biocatalysts to give the desired keratinolytic activity (Table 3). The optimal growth of microbes and enzyme production conditions occur in neutral to alkaline environments, at low temperatures (30 • C-60 • C) and under reducing conditions, which are favorable for preserving the physical and chemical quality of the hydrolyzed keratin (Fakhfakh et al, 2013;Tuysuz et al, 2021). The degradation of keratinous materials by microbes relies on the synergistic activity of several enzymes.…”

“…Keratinolytic bacteria such as B. licheniformis and Bacillus subtilis have optimal growth conditions at pH 6.0-11.0 and 30 • C−55 • C for up to ∼7 days (Kshetri et al, 2020;Tuysuz et al, 2021) -WPH showed radical scavenging activity -WPH showed chelating and reducing power of F 3+ -Fe 2+ (2005) 1 g/L sodium dodecyl sulfate, 2.6% (v/v) protease (Savinase), along with 8.6 g/L sodium hydrogen sulfite, liquor to fiber ratio of 25 ml/g for 4hr.…”

“…Keratinolytic bacteria such as B. licheniformis and Bacillus subtilis have optimal growth conditions at pH 6.0–11.0 and 30°C−55°C for up to ∼7 days (Kshetri et al., 2020; Tuysuz et al., 2021). For instance, B. subtilis DB 100 can utilize sheep wool as a sole carbon and nitrogen source, causing degradation of the wool on incubation at 30°C, pH 7.0, for 5 days (Zaghloul et al., 2011).…”

“…Additional in vitro studies have demonstrated the potential of keratin to influence the growth of microbes and consequently the type and quantity of valuable metabolites, for example, the production of single‐cell proteins, ethanol, organic acids, polysaccharides, pigments, enzymes, vitamins, and antibiotics (Arslan, 2021; Taskin et al., 2016; Tuysuz et al., 2021). Thriving using keratin as a substrate is possible for those microbes capable of using keratin as a source of nitrogen.…”

An alternative peptone preparation using Hermetia illucens (Black soldier fly) hydrolysis: process optimization and performance evaluation

“…A growing body of research has begun to explore unconventional sources for peptone derivation. Materials such as wool, tuna heads, and salmon skeletons have been used with different proteases to yield peptones that demonstrate comparable bacterial growth performance to their commercially available counterparts ( Broli et al, 2021 ; Tuysuz et al, 2021 ; Vázquez et al, 2022 ). HI are able to grow and mature at a fast growth rate which leads to a high yield of larvae, HIL.…”