Combined Algal Processing provides new process options for high-value co-products from algal biomass in a single-stream process

The downstream processing of algal biomass containing lipids, carbohydrates, and proteins, typically focuses on oil extraction with carbohydrates and proteins destined for low-value anaerobic digestion. A Combined Algal Processing (CAP) strategy has been developed as a streamlined algal biomass processing option to take advantage of solubilized sugars, primarily glucose and mannose, and other nutritive components released from algal cells during acid pretreatment. Pretreated algal slurries are directly fermented prior to hexane extraction for algal lipid recovery. Yeast fermentation of pretreated algal slurry was finished within 15 hours resulting in > 85% theoretical yield of ethanol and did not require additional nutrients. In addition, due to the nutritive value of the pretreated algal slurry, additional co-products other than ethanol were investigated. One such high-value co-product, succinic acid, was produced at up to 25 g/L. Simulated distillation was used to remove the ethanol from the fermentation beer followed by hexane extraction of the whole slurry. Algal lipids were recovered at 70 to 87% efficiency post-fermentation. Thus consolidated algal processing and fermentation technology provides significant improvements in algal biomass utilization in an integrated biorefinery setting and provides process options for a range of value-added fermentative co-products.