Cellulases are industrially important hydrolytic enzymes that are applicable in the bioconversion of cellulosic biomass to simple sugars. In this work, Pichia pastoris carrying an endoglucanase cDNA (CMC3) from a thermophilic fungus, Humicola insolens, was grown in a 30 L bioreactor to produce recombinant CMC3 in a fed-batch cultivation mode. After optimisation of the cultivation conditions, a total of 5.3 gL-1 proteins were obtained in a 20 L working volume after a 40 h induction with methanol. CMC3 expresses a β-1,4-endoglucanase with a specific activity of 62.83 U mg-1, demonstrating its specificity for hydrolysing carboxymethyl cellulose as a substrate. No detectable hydrolysis on Sigmacell® cellulose, Avicel or beechwood xylan was observed. The recombinant CMC3 displayed moderate thermostability, being stable at up to 50°C for more than 72 h. Metal ions such as Mn²+ and Co²+ enhanced the CMC3 activity, while Ni+, Zn²+ and Cu²+ inhibited the enzyme activity. The CMC3 produced in P. pastoris was stable under long-term storage, retaining 84% and 75% of its initial activity after 4 months of storage at 4°C and 25°C, respectively. The addition of stabilisers further improved the enzyme stability by 7% and 5% at 4°C and 25°C, respectively.