Pretreatment for Simultaneous Production of Total Lipids and Fermentable Sugars from Marine Alga, Chlorella sp.

Abstract

The goal of this study was to determine the optimal pretreatment process for the extraction of lipids and reducing sugars to facilitate the simultaneous production of biodiesel and bioethanol from the marine microalga Chorella sp. With a single pretreatment process, the optimal ultrasonication pretreatment process was 10 min at 47 KHz, and extraction yields of 6.5 and 7.1 (percentage, w/w) of the lipids and reducing sugars, respectively, were obtained. The optimal microwave pretreatment process was 10 min at 2,450 MHz, and extraction yields of 6.6 and 7.0 (percentage, w/w) of the lipids and reducing sugars, respectively, were obtained. Lastly, the optimal high-pressure homogenization pretreatment process was two cycles at a pressure of 20,000 psi, and extraction yields of 12.5 and 12.8 (percentage, w/w) of the lipids and reducing sugars, respectively, were obtained. However, because the single pretreatment processes did not markedly improve the extraction yields compared to the results of previous studies, a combination of two pretreatment processes was applied. The yields of lipids and reducing sugars from the combined application of the high-pressure homogenization process and the microwave process were 24.4 and 24.9 % (w/w), respectively, which was up to three times greater than the yields obtained using the single pretreatment processes. Furthermore, the oleic acid content, which is a fatty acid suitable for biodiesel production, was 23.39 % of the fatty acids (w/w). The contents of glucose and xylose, which are among the fermentable sugars useful for bioethanol production, were 77.5 and 13.3 % (w/w) of the fermentable sugars, respectively, suggesting the possibility of simultaneously producing biodiesel and bioethanol. Based on the results of this study, the combined application of the high-pressure homogenization and microwave pretreatment processes is the optimal method to increase the extraction yields of lipids and reducing sugars that are essential for the simultaneous production of biodiesel and bioethanol.

Investigation of the effects of microalgal cell concentration and electroporation, microwave and ultrasonication on lipid extraction efficiency

“…Ma et al, 2014 [14] reported the increase in extraction yield resulting from microwaves was equal to the increase in yield from ultrasonication, which is consistent with this study. In prior studies, the increase in yield ranged from 30% [10] to 120% [8] for ultrasonication and from 40% [14] to 600% [15] for microwaves. These studies used different solvent ratios, that may not have been as ideal as those prescribed by Bligh and Dyer, and the benefits of pretreatment may have been greater for less efficient solvents.…”

“…Therefore, the TIs used above were selected based on results reported in prior studies for electroporation [22], ultrasonication [10,12], and microwave [14,15].…”

“…These studies reported a significant increase in the quantity of lipids extracted due to pretreatment. For ultrasonication, the percent increase ranged from 30% [10] to 400% [8] with a mean and median of 136% and 99%, respectively. The percent increase for microwaves ranged from 38% [14] to 606% [15] with a mean and median of 288% and 150%, respectively.…”

Effective production of bioenergy from marineChlorellasp. by high-pressure homogenization

“…cells ranges from 20% to 26% in autotrophic conditions, which is the amount of sugar required for the production of bio-ethanol. [5] Therefore, we believe that due to their lipid and sugar content, these cells could be used for the co-production of biofuels. [5] However, marine microalgae have a two-layered cell wall consisting of outer and inner cell walls.…”

“…[5] Therefore, we believe that due to their lipid and sugar content, these cells could be used for the co-production of biofuels. [5] However, marine microalgae have a two-layered cell wall consisting of outer and inner cell walls. Of these two, the outer cell wall has a trilaminar structure of mixed multilayers that include cellulose.…”