High-productivity lipid production using mixed trophic state cultivation of Auxenochlorella (Chlorella) protothecoides

Abstract

A mixed trophic state production process for algal lipids for use as feedstock for renewable biofuel production was developed and deployed at subpilot scale using a green microalga, Auxenochlorella (Chlorella) protothecoides. The process is composed of two separate stages: (1) the photoautotrophic stage, focused on biomass production in open ponds, and (2) the heterotrophic stage focused on lipid production and accumulation in aerobic bioreactors using fixed carbon substrates (e.g., sugar). The process achieved biomass and lipid productivities of 0.5 and 0.27 g/L/h that were, respectively, over 250 and 670 times higher than those obtained from the photoautotrophic cultivation stage. The biomass oil content (over 60% w/DCW) following the two-stage process was predominantly monounsaturated fatty acids (~82%) and largely free of contaminating pigments that is more suitable for biodiesel production than photosynthetically generated lipid. Similar process performances were obtained using cassava hydrolysate as an alternative feedstock to glucose.

Effects of Monochromatic Illumination with LEDs Lights on the Growth and Photosynthetic Performance of Auxenochlorella protothecoides in Photo- and Mixotrophic Conditions

“…Regarding lipid content, it was found that higher availability of nitrogen in the photoautotrophic cultures resulted in higher lipid content (p < 0.05). These results are not in line with other studies on A. protothecoides, which report lipid contents of more than 50% [35,36]. It appears that the strain used in this study under the specific conditions resulted in the accumulation either of proteins (when grown under nitrogen replete conditions) or carbohydrates (when grown under low nitrogen availability).…”

Continuous Culture of Auxenochlorella protothecoides on Biodiesel Derived Glycerol under Mixotrophic and Heterotrophic Conditions: Growth Parameters and Biochemical Composition

“…Oleic acid (C18:1 up to 55.6%), linoleic (C18:2 up to 19.8%), and palmitic acid (C16:0 up to 12.5%) were the major components of all the three oil categories and contributed more than approximately 85% to the total fatty acids. Similar results for lipid biosynthesis were observed by Rismani-Yazdi et al [ 48 ] during the cultivation of A. protothecoides in a heterotrophic semicontinuous system in glucose. In the present study, there were no significant differences in the fatty acids profiles between the two trophic modes applied.…”

“…Namely, under mixotrophic conditions, the percentages of the major fatty acids produced were: 61.2% for oleic, 18.8% for linoleic, and 11.4% for palmitic acid. Rismani-Yazdi et al [48], in contrast, observed different fatty acid compositions between photoautotrophically and heterotrophi- Fourteen different types of fatty acids, including saturated, monounsaturated, and polyunsaturated, were detected in the heterotrophic mode culture. Oleic acid (C18:1 up to 55.6%), linoleic (C18:2 up to 19.8%), and palmitic acid (C16:0 up to 12.5%) were the major components of all the three oil categories and contributed more than approximately 85% to the total fatty acids.…”

Techno‐economic assessment of heterotrophic microalgae biodiesel production integrated with a sugarcane bio‐refinery

“…In heterotrophic cultivation, organic carbon is instead utilized as a structural and energy source and no light is needed to support growth. Thus, heterotrophic organisms can grow in closed bioreactors, reaching biomass concentrations up to 100 g L −1 12–14 and lipid productivities as high as 10–15 g L −1 d −1 15 (Table S1 ‐ Supplementary data). Such biomass concentrations are about 100 times higher than those obtained in autotrophic cultivation, which reduces dilution and harvesting costs.…”