Evaluation of the Bacillus cereus Strain 1-p Protease for the Unhairing of Goatskins during Leather Production

Abstract

The unhairing stage of leather processing is associated with the production of significant amounts of solid and liquid wastes. The use of enzymes to replace the polluting sulphides currently used for unhairing is a viable alternative. Various proteases from different Bacillus cereus strains as well as many other bacterial strains have been used successfully for the unhairing of skins. However, no previous work has assessed the use of the crude alkaline protease extract from Bacillus cereus strain 1-p, a novel Bacillus cereus strain obtained from the shores of Lake Bogoria - a soda lake in Kenya – in the unhairing of goatskins. This study, therefore, evaluates the potential of the protease extract from the Bacillus cereus strain 1-p to unhair goatskins. Optimum variables for unhairing using the protease were investigated. Complete unhairing was achieved within 12 hours at 27°C and pH 12 using the crude enzyme. The period and temperature required for complete unhairing were significantly lower than that of other enzymatic unhairing techniques. Compared to the leather unhaired with sulphide, the leather unhaired with the enzyme did not only show superior organoleptic properties but also recorded comparable or superior physical properties, namely tensile strength (26.94 N/mm2), percentage elongation (76.29%), tear strength (43.59 N/mm), and distension at grain crack and burst (7.9 mm and 8.2 mm respectively). The wastewater from the enzymatic unhairing process recorded a significant reduction in biochemical oxygen demand (78%), chemical oxygen demand (83%), and the wastewater volume (50%) compared to the process that uses sulphide. It was concluded that the use of the crude protease extract from the Bacillus cereus strain 1-p in unhairing goatskins is feasible.

Pre-tanning of Goatskin by Minimizing Chemical Usage using Crude Protease Enzyme for Crust Leather Preparation

“…Pollution load generation during unhairing in terms of TDS, TSS, and EC.Lime and sul de are two examples of the kinds of chemicals that can contribute to the creation of high-alkaline sludge, which is a major contributor to environmental pollution. These ndings are in agreement with the previous studies(Nyakundi et al 2021). The utilization of enzymatic processes eliminates…”

“…Although some research used goatskins in their entirety, others did not (Nyakundi et al 2021;Shaikh et al 2019). However, it's crucial to note that Nyakundi et al's method of unhairing wasn't entirely free from lime, casting a shadow of doubt on potential lime-related pollution concerns.…”

Enzymatic dehairing of sheep skin: Recovery and characterization of commercially important wool hydrolysate and fats

“…High temperatures cause skin degradation and deterioration of leather quality. In this study, the temperature was varied from 22 ºC, and 35 ºC, as recommended in the literature (Covington & Wise, 2019;Nyakundi et al, 2021). The effectof temperature on wool removal by the crude protease at the optimum pH was evaluated at 22 ºC, 25 ºC, 30 ºC, and 35ºC (Figure 3).…”

“…Under highly alkaline pH, the shrinkage temperature is 50 °C or even lower. The recommended dehairing temperature is therefore 30 ºC or less (Covington & Wise, 2019;Nyakundi et al, 2021). The optimal temperature of 30 ºC, was therefore adopted for maximum protease activity for the enzyme derived from bacillus cereus strain 1-p.…”

Proceedings of the 9th International Conference on Advanced Materials and Systems

“…Proteases are the most important extensively utilized enzymes for dehairing hides and skins. Some researchers have utilized them in rehydration, pickling, soaking, and chrome tanning (Nyakundi et al, 2021). Proteases differ in terms of substrate selectivity, working pH, catalytic activity, working temperature, active site specificity, stability profiles, and other characteristics (Kumar et al, 1999).…”