The industrial application of lactic acid is very broad; hence, the high demand is forecasted to multiply in the future. This review presented the major problems for the efficient production of lactic acid from lignocellulose biomass using lactic acid bacteria (LAB) and further proposes three promising solutions to solve these problems, exposing their potentials and future research needs. Recombinant cellulolytic strategy in LAB promises a significant reduction of lactic acid production costs, however, extensive research on genetic engineering is still needed. Microwave‐assisted deep eutectic solvent pretreatment is extremely fast and produces little to no harmful by‐products, but it has not been investigated for lactic acid production yet. Continuous simultaneous saccharification and fermentation with enzyme and cell recycle is newly proposed by the authors as a process set up that can solve the problems of feedback‐, substrate‐ and end‐product inhibition while resulting in higher lactic acid productivities, yield, and concentration.

Microalgae are becoming sustainable alternative feedstocks to food crops for biodiesel production which can also solve the problems associated with the use of fossil fuels. However, several challenges about microalgae’s cultivation, harvesting, pre-treatment and extraction processes as well as the technology of biodiesel production affect its sustainability. This study proffers solutions to these challenges and recommended that hybrid culture systems with genetically engineered microalgal species would overcome the challenges of cultivation. The coagulation/flocculation method was adjudged the best harvesting process of the microalgae for its sustainability for biodiesel production. The pre-treatment by ultrasound coupled with enzymatic extraction was suggested best, due to their numerous advantages over other methods. A novel integrated ultrasound-enzyme-enzyme in-situ pre-treatment-extraction-transesterification design is considered a sustainable approach to utilising microalgae biomass for biodiesel production. The study concludes that the microalgae biomass is more than sufficient to meet the global energy demand and can be economically harnessed as a sustainable feedstock for biodiesel production. HIGHLIGHTS •Microalgae contain sufficient characteristics for their sustainability for biodiesel production.• Implementation of genetic strategies of microalgal species by cultivating in a hybrid system is the key to microalgae sustainability.• Harvesting of microalgae by coagulation/flocculation method would promote its efficient lipid recovery.• Microalgae are novel feedstocks with a rigid cell wall, its lipid extraction requires the use of effective and efficient pre-treatment.• The ultrasound-enzymatic extraction and enzymatic transesterification in an in-situ process can sustainably utilise microalgae biomass for biodiesel production.