Abstract
Keratin is a tough fibrous structural protein that is difficult to digest with pepsin and trypsin because of the presence of a large number of disulfide bonds. Keratin is widely found in agricultural waste. In recent years, especially, the development of the poultry industry has resulted in a large accumulation of feather keratin resources, which seriously pollute the environment. Keratinase can specifically attack disulfide bridges in keratin, converting them from complex to simplified forms. The keratinase thermal stability has drawn attention to various biotechnological industries. It is significant to identify keratinases and improve their thermostability from microorganism in extreme environments. In this study, the keratinases DgoKerA was identified in Deinococcus gobiensis I-0 from the Gobi desert. The amino acid sequence analysis revealed that DgoKerA was 58.68% identical to the keratinase MtaKerA from M. thermophila WR-220 and 40.94% identical to the classical BliKerA sequence from B. licheniformis PWD-1. In vitro enzyme activity analysis showed that DgoKerA exhibited an optimum temperature of 60 °C, an optimum pH of 7 and a specific enzyme activity of 51147 U/mg. DgoKerA can degrade intact feathers at 60 °C and has good potential for industrial applications. The molecular modification of DgoKerA was also carried out using site-directed mutagenesis, in which the mutant A350S enzyme activity was increased by nearly 30%, and the results provide a theoretical basis for the development and optimization of keratinase applications.
Highlights
The molecular modification of DgoKerA was carried out using site-directed mutagenesis, in which the mutant A350S enzyme activity was increased by nearly 30%, and the results provide a theoretical basis for the development and optimization of keratinase applications
Phylogenetic analysis of DgoKerA and other homologous keratinases was constructed based on the amino acid sequence
The keratinase DgoKerA was identified from the genome of D. gobiensis
Summary
Keratin is rich in nutrients and contains up to 70% of various amino acids, such as cysteine, lysine, proline and serine, which makes it a potentially valuable protein [1]. Keratin is difficult to degrade and utilize due to the strong properties conferred by the huge cross-linking of disulfide and hydrogen bonds, and the recycling of keratin of animal origin, which is produced by the poultry industry at over 1 billion tons per year, has become a challenge for the industry [2,3]. Keratinase acts on the disulfide bonds of keratin and, hydrolyses keratin [4]. Keratinases are widely found in microorganisms and the use of keratinases to recover keratin-related resources is an environmentally friendly, low energy consuming and sustainable approach [5]
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