The continuous rise in crude oil prices, coupled with environmental concerns surrounding greenhouse gas emissions, has spurred growing interest in bioethanol as a renewable fuel alternative. Lignocellulosic biomass—such as straw, softwood, sugarcane bagasse, corncob, fruit waste, and algal sources—has emerged as a promising feedstock due to its abundance, low cost, and rich carbohydrate composition. Efficient and economical production of bioethanol from such materials requires optimized pretreatment methods, minimized process costs, and the application of high-yield or genetically engineered microbial strains. Pretreatment techniques range from enzymatic and chemical (acidic or alkaline) to physical methods like autoclaving and ultrasonication, with microbial enzymes from fungi and bacteria offering eco-friendly alternatives. Co-culturing fermentative yeasts such as Saccharomyces cerevisiae with cellulase- and xylanase-producing fungi like Aspergillus, Trichoderma, and Pichia can enhance sugar release and ethanol yield through synergistic enzymatic activity. Effective co-cultivation depends on microbial compatibility and precise control of fermentation conditions. This review explores the impact of various co-culture strategies—particularly involving S. cerevisiae and cellulolytic or xylosefermenting microorganisms—on bioethanol production from diverse lignocellulosic substrates.
