Mallick Nirupama, Bagchi Sourav K, Koley Shankha, Singh Akhilesh K
Agricultural and Food Engineering Department, Indian Institute of Technology Kharagpur, Kharagpur India.
Amity Institute of Biotechnology, Amity University at Lucknow, Lucknow India.
Front Microbiol. 2016 Jun 30;7:1019. doi: 10.3389/fmicb.2016.01019. eCollection 2016.
The last decade has witnessed a tremendous impetus on biofuel research due to the irreversible diminution of fossil fuel reserves for enormous demands of transportation vis-a-vis escalating emissions of green house gasses (GHGs) into the atmosphere. With an imperative need of CO2 reduction and considering the declining status of crude oil, governments in various countries have not only diverted substantial funds for biofuel projects but also have introduced incentives to vendors that produce biofuels. Currently, biodiesel production from microalgal biomass has drawn an immense importance with the potential to exclude high-quality agricultural land use and food safe-keeping issues. Moreover, microalgae can grow in seawater or wastewater and microalgal oil can exceed 50-60% (dry cell weight) as compared with some best agricultural oil crops of only 5-10% oil content. Globally, microalgae are the highest biomass producers and neutral lipid accumulators contending any other terrestrial oil crops. However, there remain many hurdles in each and every step, starting from strain selection and lipid accumulation/yield, algae mass cultivation followed by the downstream processes such as harvesting, drying, oil extraction, and biodiesel conversion (transesterification), and overall, the cost of production. Isolation and screening of oleaginous microalgae is one pivotal important upstream factor which should be addressed according to the need of freshwater or marine algae with a consideration that wild-type indigenous isolate can be the best suited for the laboratory to large scale exploitation. Nowadays, a large number of literature on microalgal biodiesel production are available, but none of those illustrate a detailed step-wise description with the pros and cons of the upstream and downstream processes of biodiesel production from microalgae. Specifically, harvesting and drying constitute more than 50% of the total production costs; however, there are quite a less number of detailed study reports available. In this review, a pragmatic and critical analysis was tried to put forward with the on-going researches on isolation and screening of oleaginous microalgae, microalgal large scale cultivation, biomass harvesting, drying, lipid extraction and finally biodiesel production.
在过去十年中,由于化石燃料储备因交通运输的巨大需求而不可逆转地减少,同时温室气体(GHG)向大气中的排放量不断增加,生物燃料研究获得了巨大的推动力。鉴于迫切需要减少二氧化碳排放,并考虑到原油地位的下降,各国政府不仅为生物燃料项目投入了大量资金,还为生产生物燃料的供应商提供了激励措施。目前,利用微藻生物质生产生物柴油已变得极为重要,因为它有可能避免优质农业土地使用和食品安全问题。此外,微藻可以在海水或废水中生长,与一些最佳的含油量仅为5%-10%的农业油料作物相比,微藻油含量可超过50%-60%(干细胞重量)。在全球范围内,微藻是最高产的生物质生产者和中性脂质积累者,超过任何其他陆地油料作物。然而,从菌株选择和脂质积累/产量、藻类大规模培养,到收获、干燥、油提取和生物柴油转化(酯交换)等下游过程,乃至整个生产过程,每一步都存在许多障碍。产油微藻的分离和筛选是一个关键的上游因素,应根据淡水或海洋藻类的需求来解决,同时要考虑到野生型本地分离株可能最适合从实验室到大规模开发的应用。如今,有大量关于微藻生物柴油生产的文献,但没有一篇详细描述了微藻生物柴油生产上下游过程的具体步骤及其优缺点。具体而言,收获和干燥占总生产成本的50%以上;然而,详细的研究报告却相当少。在这篇综述中,我们试图对正在进行的产油微藻分离和筛选、微藻大规模培养、生物质收获、干燥、脂质提取以及最终生物柴油生产的研究进行务实和批判性分析。