A Seagrass-Based Biorefinery for Generation of Single-Cell Oils for Biofuel and Oleochemical Production

Abstract

78 million tons of residual seagrass deposits accumulate annually on shorelines worldwide. These represent an untapped feedstock for fermentative single-cell oil production, targeted at biofuel and oleochemical generation, without affecting the sensitive marine environment or compromising food security. Seven beach-cast samples of seagrass (related to Z. marina, Z. noltii, S. filiforme, P. australis, P. oceanic, and T. testudinum) were collected from marine ecosystems around the world. A combination of 18S rRNA phylogenetic, structural, and comprehensive biomass analyses of seagrass leaves were applied. The carbohydrate content ranged from 73 to 81 % (w/dwbiomass). Single-step enzymatic hydrolysis was developed to efficiently release the monomeric sugars contained in seagrasses biomass without any pretreatment. P. oceanica hydrolysate allowed for higher lipid yields (6.8 g L−1) compared to the synthetic minimal medium (5.1 g L−1) in shake flasks, and was subsequently utilized as the sole fermentation medium for oleaginous yeast T. oleaginosus at a technical scale using a fed-batch bioreactor, which provided 24.5 g L−1 lipids (0.35 g L−1 h−1). Moreover, the sugar/lipid conversion ratio was 0.41 (w/w). Cumulative data indicates that by exploiting only half of the global beach-cast seagrass, approximately 4 million tons of microbial oils could be generated.