Biorefinery concept of simultaneous saccharification and co-fermentation: Challenges and improvements

•Process intensification of SSCF for commercial use.•Engineering of microbes for higher saccharification rate.•Impeller designing and pathway engineering for co-fermentation improvement.•Role of conditional factors and challenges for optimizing the process. Bioethanol is an alternative to motor fuel, generated through the fermentation of sugars released from the hydrolyzed cellulosic material. For efficient ethanol production, total utilization of sugars needs an improved fermentation approach i.e. Simultaneous Saccharification and Co-fermentation (SSCF). SSCF is the current, advanced, close to commercialization approach that is being continuously improved for high ethanol titer, total sugar (hexose + pentose) utilization, high mass transfer, reducing the feedback inhibition, and one-pot conversion strategies. The major improvement strategies such as enhancing the saccharification rate, engineering microbes for co-fermentation, enhancing mass transfer through impeller designing, and the role of conditional factors on the SSCF process are reviewed in this study. [Display omitted]