Effect of operational parameters on methanol biofiltration coupled with Endochitinase 42 production

• A maximum elimination capacity of 643 g m−3 h−1 and Ech42 activity of 1020 U L−1 were obtained.
• The highest enzymatic activity was obtained at 7.5 g L−1 ammonium sulfate, pH 5, and an EBRT of 60 s.
• Nitrogen concentration was a limiting factor for methanol degradation and Ech42 production.

Biofiltration is a technology for the biological degradation of multiple gas pollutants. It consists of a biological active bed where the contaminant gas is vented through and aerobically degraded. In this study, a novel methanol biofiltration process coupled with the production of the heterologous protein Endochitinase-42, using a genetically modified Pichia pastoris strain, was investigated. Three identical biofilters of 3.3 L packed with Perlite were operated under discontinuing addition of nutritive solution. Four important parameters such as methanol inlet loading rate (ILR), pH, nitrogen concentration, and empty bed residence time (EBRT) were studied. Evaluation of ILR resulted in a maximum elimination capacity (EC) of 643 g m−3 h−1 and heterologous Ech42 activity of 1020 U L−1. In another stage, it was observed that nitrogen is a limiting factor not only for methanol degradation, but also for protein production, being 7.5 g L−1 ammonium sulfate (7 gC/gN) the optimal value with a protein activity of 1172 U L−1. Moreover, pH 5.5 and EBRT of 60 s were the most favorable values for enzymatic production. In general, a set of operational conditions, including 7.5 g L−1 ammonium sulfate, pH 5, and EBRT of 60 s were optimal to maximize the enzymatic productivity.

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