Enhancing carbohydrate repartitioning into lipid and carotenoid by disruption of microalgae starch debranching enzyme.

Kato, Yuichi; Oyama, Tomoki; Inokuma, Kentaro; Vavricka, Christopher J.; Matsuda, Mami; Hidese, Ryota; Satoh, Katsuya; Oono, Yutaka; Chang, Jo-Shu; Hasunuma, Tomohisa; Kondo, Akihiko

Light/dark cycling is an inherent condition of outdoor microalgae cultivation, but is often unfavorable for lipid accumulation. This study aims to identify promising targets for metabolic engineering of improved lipid accumulation under outdoor conditions. Consequently, the lipid-rich mutant Chlamydomonas sp. KOR1 was developed through light/dark-conditioned screening. During dark periods with depressed CO2 fixation, KOR1 shows rapid carbohydrate degradation together with increased lipid and carotenoid contents. KOR1 was subsequently characterized with extensive mutation of the ISA1 gene encoding a starch debranching enzyme (DBE). Dynamic time-course profiling and metabolomics reveal dramatic changes in KOR1 metabolism throughout light/dark cycles. During light periods, increased flux from CO2 through glycolytic intermediates is directly observed to accompany enhanced formation of small starch-like particles, which are then efficiently repartitioned in the next dark cycle. This study demonstrates that disruption of DBE can improve biofuel production under light/dark conditions, through accelerated carbohydrate repartitioning into lipid and carotenoid. Kato et al. describe the isolation of a mutant Chlamydomonas sp. KOR1 that accumulates lipid even during diurnal cycles and has extensive mutations in the ISA1 gene encoding a starch debranching enzyme (DBE). They further demonstrate that disruption of DBE can improve biofuel production under light/dark conditions, through accelerated carbohydrate repartitioning into lipid and carotenoid.

CARBOHYDRATES; CAROTENOIDS; MICROALGAE; GENETIC mutation; METABOLOMICS

Communications Biology, 2021, Vol 4, Issue 1, p1

2399-3642

Academic Journal

10.1038/s42003-021-01976-8