Developing biological processes for ulvan and microbial oil production from Ulva lactuca

Algae have been considered as potential feedstock for biofuel production because of their productivity, possibility of additional services and high value co-products. Nevertheless, in comparison to the research on microalgae, less attention has been paid to the properties of macroalgae and the associated biological processes required to utilize macroalgal biomass. In the present work, the wet storage of Ulva lactuca by ensilage and the utilization of Ulva silage as feedstock for bioprodutions of ulvan and microbial oil were investigated. For the first part of this work, the additions of cell wall digesting enzyme and lactic acid bacteria (LAB) were studied for their effects and optimal loading amount on the ensilage of Ulva lactuca. The objective was to preserve the carbohydrate content in the biomass of Ulva lactuca. The results showed that both enzyme addition and LAB addition had significant effects on the pH reduction and lactic acid content of the silage. The results also showed that the Ulva silage were relatively easier to be extracted by hot water and hydrolyzed by diluted acid than raw Ulva biomass for ulvan and fermentable productions. The dilute acid hydrolysate of Ulva silage was subjected to heterotrophic cultivation of various microorganisms for microbial oil production. Moreover, the ulvan extracted from the Ulva silage was analyzed for its biochemical properties. Finally, an integrated biorefinery process of Ulva lactuca was proposed based on the findings of this work.