Abstract
BackgroundLignocellulosic biomass has long been recognized as a potential sustainable source of sugars for biofuels. However, many physicochemical structural and compositional factors inhibit the enzymatic digestibility of the lignocellulosic biomass. In this study, efficient pretreatment method of rice straw (RS) was developed and the RS hydrolysate was applied in the cultivation of microalgae for lipid production.ResultsGamma ray irradiation (GRI) and alkali solution were used for the pretreatment, and saccharification was carried out with lignocellulolytic enzymes. When RS was pretreated by combined GRI and alkali method, the glucose and xylose saccharification yield after enzymatic hydrolysis increased up to 91.65 and 98.84 %, respectively. The enzymatic hydrolysate from the RS pretreated with the combined method was used to cultivate Chlorella protothecoides for lipid production. The maximum concentrations of biomass and fatty acid methyl ester of cells were 6.51 and 2.95 g/L, respectively. The lipid content of C. protothecoides from RS hydrolysate was comparable to that from glucose, and the lipid composition was similar between different carbon sources.ConclusionThese results demonstrate that the combined pretreatment with gamma irradiation was highly effective in preparing hydrolysate, and the rice straw hydrolysate could be used as an alternative carbon source for microalgal lipid production for biofuel.
Highlights
Lignocellulosic biomass has long been recognized as a potential sustainable source of sugars for biofuels
We demonstrated the effectiveness of a combined pretreatment method using gamma ray irradiation (GRI) and low concentration of aqueous alkali solution (1 % NaOH) in enhancing the enzymatic digestibility of rice straw (RS)
In this study, rice straw was investigated for the production of lipid from microalgae
Summary
Lignocellulosic biomass has long been recognized as a potential sustainable source of sugars for biofuels. Joe et al Biotechnol Biofuels (2015) 8:125 reports on various pretreatment options, none of them can be considered as the ideal option because the choice of optimal pretreatment method depends on the type of biomass, and its economic and environmental impact [7]. Irradiation reduced the crystallinity of lignocellulose biomass, leading to a decrease in the degree of polymerization and increase in the surface area, which in turn increase the enzyme accessibility and enzymatic digestibility. For this reason, irradiation pretreatment has been investigated for decades as a physical pretreatment method of biomass [8–13]. More research on irradiation pretreatment in combination with other pretreatment methods should be conducted to make this option economically viable
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