Alkaliphilic microbial cellulases: sources, structural insights, and bioengineering approaches for industrial...

As the biofuel/biorefinery/green economy advances quickly, the need for durable cellulases to operate under varying conditions in the industrial sector has increased. A specific type of cellulase that has emerged from this demand is alkaliphilic cellulase (ALKC). Due to their stability and high catalytic activity at elevated pH ranges (e.g., pH 8-11), ALKCs are being developed as biocatalysts for alkaline pretreatment and other harsh, high-pH industrial processes.The purpose of this review is to provide an updated overview of ALKCs focusing on their microbial origins, structural characteristics, and modes of action; it will summarize how ALKCs can be used in numerous applications including: the conversion of lignocellulosic biomass into biofuels; pulp and paper production; formulation of laundry detergents; textile bioprocessing; and waste management. Integrating ALKCs into modern biorefineries will be beneficial to society by decreasing the overall amount of chemicals needed in a bioprocess (and their associated costs), reducing water usage, and increasing the efficiency of the process. Significant advances in enzyme engineering, synthetic biology, and designer cellulosomes have all contributed to the enhanced catalytic performance, stability, and substrate specificity of ALKCs. Despite the benefits that would result from their use, there remain significant impediments to the large-scale application of ALKCs; their long-term stability, incompatibility with conventional fermentation systems, and lack of standardised methods for measuring activity are among these barriers. In order for ALKCs to be employed at industrial levels and used to their full potential in sustainable bioprocessing, these identified constraints will require resolution.