Screening Microalgae Strains for Biodiesel Production: Lipid Productivity and Estimation of Fuel Quality Based on Fatty Acids Profiles as Selective Criteria

Abstract

The viability of algae-based biodiesel industry depends on the selection of adequate strains in regard to profitable yields and oil quality. This work aimed to bioprospecting and screening 12 microalgae strains by applying, as selective criteria, the volumetric lipid productivity and the fatty acid profiles, used for estimating the biodiesel fuel properties. Volumetric lipid productivity varied among strains from 22.61 to 204.91 mg l −1 day −1 . The highest lipid yields were observed for Chlorella (204.91 mg l −1 day 1 ) and Botryococcus strains (112.43 and 98.00 mg l −1 day −1 for Botryococcus braunii and Botryococcus terribilis, respectively). Cluster and principal components analysis analysis applied to fatty acid methyl esters (FAME) profiles discriminated three different microalgae groups according to their potential for biodiesel production. Kirchneriella lunaris, Ankistrodesmus fusiformis, Chlamydocapsa bacillus, and Ankistrodesmus falcatus showed the highest levels of polyunsaturated FAME, which incurs in the production of biodiesels with the lowest (42.47-50.52) cetane number (CN), the highest (101.33-136.97) iodine values (IV), and the lowest oxidation stability. The higher levels of saturated FAME in the oils of Chlamydomonas sp. and Scenedesmus obliquus indicated them as source of biodiesel with higher oxidation stability, higher ). The third group, except for the Trebouxyophyceae strains that appeared in isolation, are composed by microalgae that generate biodiesel of intermediate values for CN, IV, and oxidation stability, related to their levels of saturated and monosaturated lipids. Thus, in this research, FAME profiling suggested that the best approach for generating a microalgae-biodiesel of top quality is by mixing the oils of distinct cell cultures.

Microalgal Species Selection for Biodiesel Production Based on Fuel Properties Derived from Fatty Acid Profiles

“…Table 1. Growth media, cultivation temperature, total lipid and total fatty acid content of nine microalgal species from this study and twelve green microalgal species from [12].…”

“…: not determined; dwt: dry weight; * total fatty acid content (mg g −1 dwt) for the twelve species from [12] was calculated based on information provided in Table 3 in [12]. provided by cool white fluorescent lights at 25 °C.…”

“…Even though lipid content and FAME profiles can be variable for the same algal strain, algal species selection remains one of the most important steps to reduce cost and time for large-scale cultivation for biodiesel production [12,13]. Researchers have made efforts to find convenient and useful methods to predict key fuel properties from fatty acid profiles.…”

“…These microalgae were ranked based on the calculated key fuel properties; CN, IV, CFPP, density (υ), kinematic viscosity (ρ), and higher heating value (HHV), derived from their FAME profiles to identify the most suitable microalgal species for biodiesel production. The FAME profiles of twelve additional microalgal species were sourced from the literature [12] and biodiesel properties were calculated for comparison to the nine species from this study. Selection of these microalgal species for both extraction and analyses in this study and for literature comparisons was based on their ability to grow in similar subtropical environments.…”

Enhancement of Lipid Production from Ankistrodesmus sp

“…is unicellular green microalgae with the total lipid content of up to 24% [5]. Ankistrodesmusfusiformis and Ankistrodesmusfalcatus showed the high lipid content and high levels of polyunsaturated FAME, which could be used in the production of biodiesels with the lowest cetane number (42.47-50.52), the highest iodine values (101.33-136.97) and the lowest oxidation stability [6] and [7]. Ankistrodesmusfalcatus contained C16:0, C18:1 and C18:3 as their major fatty acid components.…”