Co-production of biodiesel and bioethanol using psychrophilic microalga Chlamydomonas sp. KNM0029C isolated from Arctic sea ice

Eun Jae Kim,Sanghee Kim,Se Jong Han,Han-Gu Choi

doi:10.1186/s13068-020-1660-z

Abstract

BackgroundBiofuels, generated using microalgae as sustainable energy, have received a lot of attention. Microalgae can be cultivated at low cost with CO2 and solar energy without competition from edible crops. Psychrophilic microalgae can be a suitable feedstock to produce biofuels without the environmental constraints of low temperatures, because they can grow below 10 °C. However, there is a lack of efficient strategies using psychrophilic microalgae to produce biodiesel and bioethanol. Therefore, the current study aimed to optimize the production of biodiesel and bioethanol from Arctic Chlamydomonas sp. KNM0029C at low temperatures.ResultsAfter incubation in a 20-L photobioreactor, fatty acid methyl ester (FAME) was extracted using modified FAME extraction methods, producing a maximum yield of 0.16-g FAME/g KNM0029C. Residual biomass was pretreated for bioethanol production, and the yields from different methods were compared. The highest bioethanol yield (0.22-g/g residual biomass) was obtained by pretreatment with enzyme (amyloglucosidase) after sonication. Approximately 300-mg biofuel was obtained, including 156-mg FAME biodiesel and 144-mg bioethanol per g dried cells, representing the highest recorded yield from psychrophilic microalgae.ConclusionsThis is the first to attempt at utilizing biomass from psychrophilic Arctic microalga Chlamydomonas sp. KNM0029C for the co-production of bioethanol and biodiesel, and it yielded the highest values among reported studies using psychrophilic organisms. These results can be used as a source for the efficient biofuel production using polar microalgae.

Highlights

Biofuels, generated using microalgae as sustainable energy, have received a lot of attention
According to a study by Heiden et al [18], Antarctic Fragilariopsis curta and Odontella weissflogii showed maximum growth rates at 200-μmol photon m−2s−1, but their growth rates decreased at 500 μmol photon m −2s−1
The fatty acid methyl ester (FAME) yields of Lewis’s method and modified method A were 165.4 and 156.5 mg/g dry cell weight, respectively (Fig. 4). These results suggested that FAME could be extracted from wet biomass without a significant reduction in yield (− 5.4%)

Summary

Introduction

Biofuels, generated using microalgae as sustainable energy, have received a lot of attention. Micro‐ algae can be cultivated at low cost with CO2 and solar energy without competition from edible crops. Psychrophilic microalgae can be a suitable feedstock to produce biofuels without the environmental constraints of low tempera‐ tures, because they can grow below 10 °C. Microalgae have high growth rates, efficient biofuel production rates, and a short harvesting cycle, leading to lower cost requirements than other feedstocks. Microalgae can be cultivated anywhere, including wasteland, coast, and sea, as long as photosynthesis is possible (which requires sunlight, water, and carbon dioxide). They do not compete with edible crops in terms of cultivation land or space

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