The composition of cellulolytic enzymes produced by T. reesei Rut C-30 is influenced by changing pH (Juhasz et al. 2004). An increase in p-glucosidase activity has been reported at pH 6 in comparison with a lower pH range of 4-5 (Tangnu et al. 1981; Nagieb et al. 1985). The purpose of supplied chemicals for the pH control is not limited to providing a stable environment for enzyme production but also to fulfill the requirement for the enzyme synthesis. A citric acid and aqueous ammonium hydroxide solution is used for pH control. In addition, citric acid helps by inducing cellulase production while aqueous ammonium hydroxide provides a nitrogen source for enzyme synthesis (Watson and Nelligan 1983; Kadam and Keutzer 1995).

Temperature affects the growth rate of T. reesei and xylanase production. Xylanase production was studied within the temperature range of 17°C to 37°C, and increased as temperatures approached 37°C. However, cellulase production decreases with increasing temperatures within this range. Therefore, a temperature shift could be a useful tool in the selectivity of cellulolytic enzyme production (Xiong 2004).