Abstract
The aim of this paper was to select keratin hydrolysate with bioactive properties by using the enzymatic hydrolysis of wool. Different proteolytic enzymes such as Protamex, Esperase, and Valkerase were used to break keratin molecules in light of bioactive additive preparation. The enzymatic keratin hydrolysates were assessed in terms of the physico-chemical characteristics related to the content of dry substance, total nitrogen, keratin, ash, cysteic sulphur, and cysteine. The influence of enzymatic hydrolysis on molecular weight and amino acid composition was determined by gel permeation chromatography (GPC) and gas chromatography-mass spectrometry (GC-MS) analyses. Antimicrobial activity of keratin hydrolysates was analysed against Fusarium spp., a pathogenic fungus that can decrease the quality of plants. The bioactivity of enzymatic hydrolysates was tested on maize plants and allowed us to select the keratin hydrolysates processed with the Esperase and Valkerase enzymes. The ratio of organised structures of hydrolysate peptides was analysed by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) deconvolution of the amide I band and may explain the difference in their bioactive behaviour. The most important modifications in the ATR spectra of maize leaves in correlation with the experimentally proven performance on maize development by plant length and chlorophyll index quantification were detailed. The potential of enzymatic hydrolysis to design additives with different bioactivity was shown in the case of plant growth stimulation.
Highlights
Biomass containing keratin is generated by the food industry, slaughterhouses, wool industry, and textiles at the end of their life cycle, with keratin being considered as one of the most abundant biopolymers [1]
The bioactivity of enzymatic hydrolysates was tested on maize plants and allowed us to select the keratin hydrolysates processed with the Esperase and Valkerase enzymes
The results showed that the performed hydrolyses were not as destructive for the keratin molecule as those reported for the enzymatic hydrolysates when the average particle size was reported to be 100–150 nm [36], but comparable to those of 750 nm, tested as a bioactive and biocompatible material for wound healing [34]
Summary
Biomass containing keratin is generated by the food industry, slaughterhouses, wool industry, and textiles at the end of their life cycle, with keratin being considered as one of the most abundant biopolymers [1]. Even the potential of keratin-based biomass use is significant; at present, it is burned, with a high energy consumption and harmful gas release [2]. The natural decomposition of feather and wool generates a bad odour, methane, and carbon dioxide, which are classified as greenhouse gases [3]. Wool is an excellent animal fibre composed of 82% hard keratin (α-keratin) with outstanding chemical and enzyme attack resistance due to the hierarchical structure of polypeptides stabilised in helical shape by hydrogen and hydrophobic bonds. Intramolecular and intermolecular cystine bonds are responsible for keratin insolubility and slow natural biodegradability
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