Peng Zheng, Mao Xinzhe, Zhang Juan, Du Guocheng, Chen Jian
1School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122 China.
3Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, 1800 Lihu Road, Wuxi, 214122 China.
Biotechnol Biofuels. 2020 Apr 1;13:61. doi: 10.1186/s13068-020-01700-4. eCollection 2020.
Keratin is the primary constituent of the vertebrate epidermis and epidermal appendages, as well as the main waste product generated during poultry processing from feathers, hair, scales, nails, etc. Keratin is generally hard, stubborn and difficult to hydrolyze; however, it is also inexpensive and contains more than 85% protein. Currently, tens of millions of tons of keratin waste are produced each year worldwide; however, no effective methods for the recovery of keratin waste have been reported thus far, making such research urgent. Keratinase has been reported to be useful for keratin waste recovery; however, nearly all keratinases are unable to hydrolyze keratin after they are detached from living cell systems. This may be due to low keratinase activity and lack of synergistic factors.
Herein, the keratinase gene from BBE11-1 was successfully expressed in WB600, allowing for improved activity of the recombinant keratinase KerZ1 to 45.14 KU/mL via promoter substitution and screening of the ribosome-binding sites. Further, real-time control of temperature, pH, dissolved oxygen, and feed strategy allowed the activity of KerZ1 to reach 426.60 KU/mL in a 15-L fermenter, accounting for a 3552-fold increase compared to the wild-type keratinase (120.1 U/mL). Most importantly, we proposed a method based on the synergistic action of keratinase KerZ1 and sodium sulfite, to hydrolyze feathers into amino acids. In specific, 100 g/L of feather waste can be successfully converted into 56.6% amino acids within 12 h, while supporting the production of dozens of bioactive peptides.
The activity of recombinant keratinase can be greatly enhanced via transcription and translational regulation in . The synergistic action of keratinase and sulfite can rapidly degrade feather waste and produce amino acids and polypeptides.
角蛋白是脊椎动物表皮和表皮附属器的主要成分，也是家禽加工过程中从羽毛、毛发、鳞片、指甲等产生的主要废弃物。角蛋白通常坚硬、顽固且难以水解；然而，它也价格低廉且蛋白质含量超过85%。目前，全球每年产生数千万吨角蛋白废弃物；然而，迄今为止尚未报道有效的角蛋白废弃物回收方法，因此此类研究迫在眉睫。据报道，角蛋白酶可用于回收角蛋白废弃物；然而，几乎所有角蛋白酶从活细胞系统中分离后都无法水解角蛋白。这可能是由于角蛋白酶活性低和缺乏协同因子。
在此，来自BBE11 - 1的角蛋白酶基因在WB600中成功表达，通过启动子替换和核糖体结合位点筛选，使重组角蛋白酶KerZ1的活性提高到45.14 KU/mL。此外，通过对温度、pH、溶解氧和补料策略的实时控制，KerZ1在15-L发酵罐中的活性达到426.60 KU/mL，与野生型角蛋白酶（120.1 U/mL）相比增加了3552倍。最重要的是，我们提出了一种基于角蛋白酶KerZ1和亚硫酸钠协同作用的方法，将羽毛水解为氨基酸。具体而言，100 g/L的羽毛废弃物可在12小时内成功转化为56.6%的氨基酸，同时支持生产数十种生物活性肽。
通过在……中的转录和翻译调控，重组角蛋白酶的活性可大大提高。角蛋白酶和亚硫酸盐的协同作用可快速降解羽毛废弃物并产生氨基酸和多肽。
