High NH₃[sbnd]N tolerance of a cheR2-deletion Rhodobacter capsulatus mutant for photo-fermentative hydrogen production using cornstalk

A mutant, JL1601, with a cheR2 gene deletion was constructed with Rhodobacter capsulatus JL1 as the wild type strain. The effects of pH, ammonia nitrogen concentration and light intensity on the photo-fermentative hydrogen production performance of JL1601 were studied. Suitable pH range for hydrogen production with the cheR2^- mutant migrated from faintly acid to weak alkaline condition, and R.capsulatus JL1601 (cheR2^-)showed higher NH₃[sbnd]N tolerance. The mutant performed better H₂ production performance than the wildtype under the same illumination condition. The maximum H₂ yield and rate of R.capsulatus JL1601 (cheR2^-)obtained to be 4406.7 ± 45.9 mL/L and 54.1 ± 1.6 mL/(L·h)with the mixture of acetate and butyrate as the carbon sources, which were increased by 36.3% and 12.3% in comparison to those of wildtype, respectively. Practical experiments using acid-enzymatic pretreated cornstalk as the carbon source indicated that, the maximum hydrogen yields by the mutant JL1601 (cheR2^-)was up to 224.85 ± 5.18 mL-H₂/g-cornstalk, which increased by 171.43% compared with that of wild type strain.