Engineered chlorophyll catabolism conferring predator resistance for microalgal biomass production.

Production of valuable compounds including biofuels and pharmaceutical precursors derived from microalgae has garnered significant interest. Stable production of algal biomass is essential to make the microalgal industry commercially feasible. However, one of the largest issues is severe biological contamination by predators grazing the algal biomass, resulting in the crash of outdoor cultures. In the present study, we propose a novel engineering strategy for microalgae to cope with predators. The overexpression of plant chlorophyllase (CLH) in a microalga resulted in the enhancement of resistance to the predator. This result supported our hypothesis that CLH promotes chlorophyll breakdown in the chloroplasts of the microalgae when they are digested by the predator, generating the phototoxic catabolite chlorophyllide that damages the predator. To the best of our knowledge, this is the first study to establish predator-resistant microalgae by enhancing the CLH activity.

Microbial production of neryl-α-D-glucopyranoside from nerol by Agrobacterium sp. M-12 reflects glucosyl transfer activity.

Terpene alcohol is widely used in perfumes and is known to possess antibacterial activity. Moreover, in its glycosylated form, it can be applied as a nonionic surfactant in food, and in the pharmaceutical, chemical, cosmetic, and detergent industries. Presently, chemical production of terpene glucosides is hampered by high costs and low yields. Here, we investigated the microbial glucosylation of nerol (cis-3,7-dimethylocta-2,6-dien-1-ol), a component of volatile oils, by Agrobacterium sp. M-12 isolated from soil. A microbial reaction using washed cells of Agrobacterium sp. M-12, 1 g/L of nerol, and 100 g/L of maltose under optimal conditions yielded 1.8 g/L of neryl-α-D-glucopyranoside after 72 h. The molar yield of neryl-α-D-glucopyranoside was 87.6%. Additionally, we report the successful transglucosylation of other monoterpene alcohols, such as geraniol, (-)-ß-citronellol, and (-)-linalool, by Agrobacterium sp. M-12. Thus, microbial glucosylation has potential widespread applicability for efficient, low-cost production of glycosylated terpene alcohols.