Monascus kaoliang CBS 302.78 immobilized in tailor-made agars as catalyst for reduction of ketones: On the quest for a green biocatalyst

After a hierarchical screening Monascus kaoliang CBS 302.78 was selected due to its high activity in the reduction of cyclic ketones. Several tailor made agars and agaroses were used in the immobilization of the fungus. The best-immobilized biocatalyst was obtained after immobilization in low methoxylated agar (A27/03) at 2.5% (w/v). The biocatalyst shape was optimized as microplates (1.27 cm × 1.27 cm × 0.31 cm). The observable modulus for external mass transfer, Ω ⋘ 1, indicates the absence of external mass transfer phenomena. The internal effectiveness factor η < 1 and the high value of the Thiele module (ϕ > 3), indicates that there is an intra-particle mass transfer restriction according to the Weisz criteria. As consequence, the kinetics of the reduction of ketones follows a formal first order kinetic model. The catalysts deactivation follows a simple exponential decay expression. Due to the renewal characteristics of the agar, the biocatalysts can be considered as green catalysts.