3.2.1. Economic Viability of Consolidated Bioprocessing

CBP is a promising strategy for effective biofuel production due to the combination of three processes (enzyme production, saccharification, and fermentation) in CBP. This strategy can reduce the reactor and the enzyme cost, which are the major impediments to low-cost biomass processing [61]. In the conventional ethanol production process, the cost by CBP production can be reduced by 25%. When considering capital, raw materials, utilities, and yield loss expenditures, a comparative cost analysis conducted on ethanol production resulted in a projection of \$0.04 gal−<sup>1</sup> for CBP. At the same time, saccharification and co-fermentation was projected at \$0.19 gal−<sup>1</sup> [64].

Despite the potential advantages that CBP represents, some limitations have not allowed bioethanol's industrial production to use this strategy. When using native organisms, the main problem is low yield and productivity despite long fermentation process periods of between 3 and 12 days [55]. In the case of using engineered modified organisms, a significant hurdle for industrial CBP organism development is achieving high levels of enzyme production without compromising ethanol productivity because there are generally problems associated with the co-expression of multiple genes other than those of interest, tolerance to the culture medium, in addition to the high cost inherent in the production of this type of organism [39,65] (Table 1).

