To explore a new method for bio-regeneration of high-protein brewery spent diatomite, an ammonifying bacteria (BSD1) was screened out from it and identified as Lysinibacillus fusiformis. The protein degradation characteristics of BSD1 was studied with rice protein as the sole nitrogen source. Maximum protein degradation activity was obtained when BSD1 was inoculated with an inoculum of 5% into a medium with glucose as carbon source and initial pH value of 7.0 and incubated at 30 degrees C for 48 h. In this optimal condition, protein concentration decreased from 156.8 mg/L to 19.2 mg/L, and protein degradation efficiency of BSD1 reached 88%. Free amino acid analysis showed that the content of Phe, Tyr, Pro, Ala, Lys, Thr and His increased in protein degradation process. After degradation, NH4+-N concentration producing in medium supernatant reached 232.2 mg/L. These results indicated the strain BSD1 could transform proteins into free amino acids and eventually convert them to ammonium or ammonia. Furthermore, strain BSD1 could also be used for deproteinization of brewery spent diatomite and 51% of proteins in spent diatomite were degraded. After biological deproteinization the specific surface area and total pore volume of diatomite improved obviously. These results illustrated that the application of strain BSD1 for bio-regeneration of high-protein brewery spent diatomite was efficient and feasible. (C) 2018, The Society for Biotechnology, Japan. All rights reserved.