Haloarchaea: green alternatives for the production of second-generation bio-ethanol using sugarcane bagasse

In light of the excessive use of fossil fuels and their associated environmental effects, more stress has been devoted to using lignocellulosic-rich resources to produce sustainable biofuel. Among lignocellulosic-rich biomass, sugarcane bagasse is a major agro-waste byproduct of the sugarcane industry. Due to high cellulose and low ash content, it has excellent potential to produce bio-ethanol. Conventional methods used for pre-treatment of lignocellulosic waste need more process efficiency and consume a large ecological footprint. Several processes in industries are carried out at high NaCl concentrations, high temperatures, and in the presence of solvents. Therefore, the scientific community has focused on halophiles for bio-ethanol production. The present review describes the use of potential lignocellulolytic haloarchaea for efficient pre-treatment and hydrolysis of sugarcane bagasse to produce bio-ethanol. Haloarchaea can increase the economic feasibility of the process since they can thrive in high salt concentration, extreme pH, elevated temperature, and low water activity conditions. Further, this review summarizes the traditionally employed strategies for the pre-treatment and hydrolysis of sugarcane bagasse, along with the latest findings on using extremophilic microbes and extremozymes. Besides this, the review explores the functional role of haloarchaea and their plant polymer degrading enzymes in acting as biocatalysts in biorefinery under extreme conditions. The integrated approach using haloarchaea to produce bio-ethanol will be technically feasible and benefit society economically and environmentally.