Identification of factors that accelerate hydrogen production by Clostridium butyricum RAK25832 using casamino acids as a nitrogen source

The ability of Clostridium butyricum RAK25832 to use casamino acids as a nitrogen source was investigated. Strain RAK25832 showed the capacity to utilize different types of carbon sources. With glucose as a carbon source (10 g/L), the preferred final concentration of casamino acids was 26.67 g/L, with a cumulative hydrogen production, production rate, and yield of 2505 mL H-2/L, 160 mL/h, and 1.81 mol H-2/mol glucose, respectively. Eighteen metal elements were screened to identify the most important metals for biohydrogen production, and four elements were optimized. The optimal medium composition was MgCl2 center dot 6H(2)O (0.1 g/L), K2HPO4 center dot 3H(2)O (6.67 g/L), NaHCO3 (2.6 g/L), and FeCL2 center dot 4H(2)O (0.002 g/L). Vitamin supplementation of the medium showed no significant effect on hydrogen production. Under the optimized conditions, cumulative hydrogen production reached 3074 mL H-2/L. This is the first study to demonstrate the use of casamino acids as a nitrogen source by C. butyricum. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.