Recovery of carbon from rice straw for simlultaneous production of protein, lipid and carbohydate by Scenedesmus sp. via mixotrophic cultivation

Abstract

Rice straw is abundantly generated as a by-product of agriculture in Vietnam. However, the material mainly contains hemicellulose and cellulose, which can be hydrolyzed to reducing sugars as a carbon source for mixotrophic production of protein-rich microalgae biomass. In this study, rice straw was obtained from local farmer and transformed to hydrolysate via separated alkaline or acid and sequential alkaline-acid treatments to evaluate sugar conversion efficiency. The hydrolysate then was used as a carbon source for cultivation of Scenedesmus sp. via mixotrophic mode. Data revealed that pretreatment with H2SO4, NaOH and combined NaOH + H2SO4 yielded sugar conversion of 12 – 13%, 11 – 12% and 22%, respectively. Scenedesmus sp. displayed a good growth performance in both rice straw hydrolysates with and without supplement of nitrogen and phosphorous, reaching the maximal optical density of 1.5 Abs in culture medium of BG-11 with 10 – 50% v/v hydrolysate. The sugar utilization efficiency by Scenedesmus sp. was determined as 70 – 94%. The Scenedesmus sp. was assayed to be rich in protein with its content of up to 45% based on dry basis. The Scenedesmus sp. biomass is potential protein source for animal and aquafeed formulation. Our preliminary results demonstrated that recovery carbon from agricultural by-product for protein-rich material for novel food development in animal food and aquafeed industries is promising.