Biochar Derived from Agricultural and Forestry Residual Biomass: Characterization and Potential Application for Enzymes Immobilization

Abstract

Very much attention has been focused on lipases as these enzymes can be used as biocatalysts, allowing a cost effective and environmentally friendly method to efficiently catalyze specific reactions. However, its application at industrial scale is still limited due to several shortcomings including low stability in their native state, inhibition by organic solvents and exhaustion of enzyme activity. To overcome these problems, lipases have been immobilized by several methods onto various supports. In this context, biochar, a low-cost material derived from the pyrolysis of residual biomass, constitutes a promising immobilization support material for enzymes due its suitable physicochemical and structural properties. In this study a complete physico-chemical and mineralogical characterization of biochar derived from pyrolyzed oat hull and pine bark at 300 and 500 � C is presented. In addition, a preliminary study on the immobilization of Candida rugosa lipase using biochar derived from oat hull pyrolyzed at 300 � C is reported. The results obtained showed that the structural and chemical properties of biochar depend on the raw materials used and pyrolysis temperature. The specific surface area (BET) presented a similar trend, increasing with an increase in pyrolysis temperature. High enrichment of trace elements such as Ba, Cr, Cu, V and Zn was detected in biochar from pine bark and was discarded for lipase immobilization purposes. The binding efficiency of lipase was in the range of 40–60%, depending on biochar particle size. The higher enzymatic activity yields were associated to small particle size of oat hull biochar. However, a reduction in Candida rugosa lipase activity yield compared with the free enzyme was obtained.