Cellulase production byAcidothermus cellulolyticus

Abstract

Acidothermus cellulolyticus, an isolate from hot springs at Yellowstone National Park, produced cellulase enzyme when grown in cellobiose-containing medium. The cellulase production, cell growth, and cellobiose degradation rates of batch culture in 2.5, 5.0, 7.5, and 10.0 g/L of cellobiose as a substrate were studied. The specific growth rates were measured, and the μ_max and K_s values based on these data were 0.2 h⁻¹ and 0.3 g cellobiose/L using the Monod equation. The maximum cellulase activities (21–69 U/L) and volumetric productivities (between 0.92 and 2.49 U/L-h) were proportional to the concentration of cellobiose.

Greatest cellulase production in batch culture was achieved by use of secondary cellulosic substrates. Mixed substrate systems consisting of 5 g/L cellobiose and various Avicel concentrations (5, 10, and 16 g/L) were also studied in batch culture. The maximum cellulase activities were53, 62, and 78 U/L, respectively. The enzyme production rate could be related to Avicel using the Monod equation. Here, maximum volumetric productivity, υ_max, was found to be 2.15 U/L-h and K_s was 7.5 g Avicel/L. Another mixed substrate system, consisting of 5 g/L cellobiose and 15 g/L Solka Floc, produced a maximum cellulase concentration of 105 U/L.