Moonnee Yeasmin Akter, Foysal Md Javed, Hashem Abu, Miah Md Faruque
Department of Genetic Engineering & Biotechnology, Shahjalal University of Science & Technology, Sylhet, 3114, Bangladesh.
School of Molecular and Life Sciences, Curtin University, Perth, WA, 6102, Australia.
J Genet Eng Biotechnol. 2021 Apr 6;19(1):53. doi: 10.1186/s43141-021-00149-8.
The leather industry generates huge volume of waste each year. Keratin is the principal constituents of this waste that is resistant to degradation. Some bacteria have the ability to degrade keratin through synthesis of a protease called keratinase that can be used as sources of animal feed and industrial production of biodiesel, biofertilizer, and bioplastic. Majority of the studies focused on keratin degradation using gram-positive bacteria. Not much of studies are currently available on production of keratinase from gram-negative bacteria and selection of best parameters for the maximum production of enzyme. The aim of this study was to isolate and characterize both groups of bacteria from soil for keratinase and optimize the production parameters.
A total of 50 isolates were used for initial screening of enzyme production in skim milk, casein, and feather meal agar. Out of 50, five isolates showed significantly higher enzyme production in preliminary screening assays. Morphological and biochemical characterization revealed 60% of the isolates as gram-negative bacteria including two highest enzyme-producing isolates. The isolates were identified as Pseudomonas aeruginosa through sequencing of 16S rRNA gene. Maximum production of enzyme from P. aeruginosa YK17 was achieved with 2% chicken feather, beef extract, and ammonium nitrate as organic and inorganic nitrogen sources and glucose as a carbon source. Further analysis revealed that 3% inoculum, 40 °C growth temperature and 72-h incubation, resulted in maximum production of keratinase.
The overall results showed significant higher production of enzyme by the P. aeruginosa YK17 that can be used for the degradation of recalcitrant keratin waste and chemical dehairing in leather industries, thereby preventing environmental pollution.
皮革行业每年产生大量废弃物。角蛋白是这种废弃物的主要成分，且难以降解。一些细菌能够通过合成一种名为角蛋白酶的蛋白酶来降解角蛋白，角蛋白酶可用于动物饲料来源以及生物柴油、生物肥料和生物塑料的工业生产。大多数研究集中在利用革兰氏阳性菌进行角蛋白降解。目前关于革兰氏阴性菌产角蛋白酶以及选择最佳参数以实现酶的最大产量的研究并不多。本研究的目的是从土壤中分离和鉴定这两类产角蛋白酶的细菌，并优化生产参数。
总共50株分离株用于在脱脂牛奶、酪蛋白和羽毛粉琼脂中进行酶产生的初步筛选。在这50株中，有5株在初步筛选试验中显示出显著更高的酶产量。形态学和生化特征表明，60%的分离株为革兰氏阴性菌，包括两株酶产量最高的分离株。通过16S rRNA基因测序，这些分离株被鉴定为铜绿假单胞菌。以2%的鸡毛、牛肉提取物和硝酸铵作为有机和无机氮源以及葡萄糖作为碳源时，铜绿假单胞菌YK17的酶产量最高。进一步分析表明，接种量为3%、生长温度为40℃和培养72小时可使角蛋白酶产量最高。
总体结果表明，铜绿假单胞菌YK17的酶产量显著更高，可用于降解顽固的角蛋白废弃物以及皮革工业中的化学脱毛，从而防止环境污染。
