bromochloroacetic-acid and sodium-sulfide

The conventional unhairing process in leather making utilises large amount of lime and sodium sulphide which is hazardous and poses serious waste disposal concerns. Under acidic conditions, sodium sulphide liberates significant quantities of hydrogen sulphide which causes frequent fatal accidents. Further, the conventional unhairing process involves destruction of the hair leading to increased levels of biological oxygen demand (BOD), chemical oxygen demand (COD), total dissolved solids (TDS) and total suspended solids (TSS) in the effluent. A safe approach is needed to overcome such environmental and health problems through an eco-benign process. The present study deals with a clean technology in which the keratinous body is detached from the dermis using enzymes produced from Bacillus crolab MTCC 5468 by solid state fermentation (SSF) as an alternative to noxious chemicals. Complete unhairing of skin could be achieved with an enzyme concentration of 1.2 % (w/w). The bio-chemical parameters of the spent liquor of the enzymatic process were environmentally favourable when compared with conventional method. The study indicates that the enzymatic unhairing is a safe process which could be used effectively in leather processing to alleviate pollution and health problems.

Topics: Bacillus; Calcium Compounds; Environmental Pollution; Hair; Hydrogen Sulfide; Keratins; Oxides; Skin; Sulfides; Tanning; Waste Disposal, Fluid

The industrial utilisation of feather keratin as a biopolymer has proven difficult due to the lack of a viable extraction technique and the poor mechanical properties of the regenerated products. Here, pure keratin films were produced from chicken feathers using sodium sulphide as sole extraction reagent in a scheme that allows films to be formed without residual chemicals. In a comparison to other films, those produced using Na2S extraction were found to be superior to other regenerated protein films and were similar to un-oriented commercial polymers. However, there was considerable variation in tensile properties between twenty repetitions of extracting and casting films which was attributed to variations in chain entanglement caused by the drying conditions. Chemical and physical treatments including crosslinking, dehydration and addition of nano-particles were investigated as means to enhance these properties. Significant increases were achieved by soaking films in isopropyl alcohol or weak acid (13 to 50% increases) or by formaldehyde or glutaraldehyde crosslinking (24 to 40% increases). The wide range of values across the pure keratin films indicates that the best route to further strength improvement may be from optimising self-assembly via controlling drying conditions, rather than from chemical treatment.

Topics: Animals; Biopolymers; Chickens; Dehydration; Feathers; Keratins; Mechanical Phenomena; Oxidation-Reduction; Sulfides