Biodegradation of wool waste and keratinase production in scale-up fermenter with different strategies by Stenotrophomonas maltophilia BBE11-1

•Wool medium was first optimized for keratinase production.•Cell growth rate did a major impact on keratinase production.•A new strategy of glucose fed-batch process was developed.•High production of keratinase with wool medium was achieved in 30-L fermenter.•Stenotrophomonas maltophilia showed great potential for waste management. A keratin-degrading strain Stenotrophomonas maltophilia BBE11-1 was grown in a 3-L batch fermenter containing wool waste as the main medium and cell growth rate was determined as the key factor to affect keratinase yield. Three strategies of temperature-shift procedure, two-stage DO control and fed-batch process were used to change growth rate. And a 62.2% improvement of keratinase yield was achieved. With the glucose fed-batch procedure in 30-L fermenter, keratinase production was significantly improved up to 117.7% (1728U/ml) as compared with initial data (793.8U/ml) in a 3-L fermenter and with much shortened fermentation time within 18h. Significant structure changes and high levels of free amino acids from wool decomposition indicated the possible applications for wool waste management and fertilizer industry. The remarkable digestion of wool cuticle also suggested its potential utilization in textile industry.