Oil-rich Biomass Research Articles

A process for biodiesel production involving the heterotrophic fermentation of Chlorella protothecoides with glycerol as the carbon source

Oil-rich biomass has been produced from heterotrophic fed-batch and semi-continuous cultures of Chlorella protothecoides in conventional 2-L stirred-tank bioreactors (STBs). The process pH is controlled by injection of CO2 and pure glycerol is the main carbon source in the culture medium. Whereas a maximum biomass concentration of 64gL−1 was achieved in fed-batch mode, semi-continuous culture at a dilution rate of 0.2day−1 yielded the best average results, with biomass and saponifiable lipid (oil) productivities of 8.7 and 4.3gL−1day−1, respectively. Both operational modes resulted in a high saponifiable oil content (>35% of dry biomass), with the highest value (around 50% of dry biomass) being obtained in semi-continuous mode. The unsaponifiable lipid content was always less than 8% (of dry biomass). These results are superior to those reported in the literature for glycerol but practically identical to those achieved with glucose. The major fatty acids (FAs) in the saponifiable lipid fraction were oleic (C18:1), linoleic (C18:2), and palmitic (C16:0), which together accounted for around 89% of the total FA content. Oleic acid was the most abundant FA, accounting for >60% of total FAs. Biodiesel was obtained using a modified process based on transesterification of wet biomass paste, with a recovery of nearly 97%. The biodiesel obtained complies with the specifications defined in current standards (ASTM Biodiesel Standard D6751in US and Standard EN 14214 in EU).

Isolation and characterization of a Scenedesmus acutus strain to be used for bioremediation of urban wastewater

Green microalgae, due to their short growth cycle and to their ability to photosynthetically fix carbon dioxide producing an oil-rich biomass, have been proposed as an attractive alternative feedstock for the production of “second generation” biofuels. However, it has been anticipated that owing to their ability to colonize very different environments characterized by high levels of nitrogen, they can also be good candidates for bioremediation, thus integrating environmental protection with sustainable biomass production. We have isolated a strain belonging to Scenedesmus genus from urban wastewater. This isolate, Scenedesmus acutus PVUW12, was tested for its ability to grow and actively deplete eutrophicating inorganic molecules present in wastewater. In order to test its biomass productivity, the PVUW12 strain was grown in a vertical-column photobioreactor using standard growth medium obtaining a maximal productivity of 0.3 g dry weight L−1 d. When the same strain was grown in the photobioreactor filled with wastewater collected from the final step of the local urban purifier plant containing 18.8 mg L−1 nitrate, we observed complete nitrogen removal coupled with a biomass production of about 0.74 g dry weight L−1 within 3 days. After 10 days, the recovered biomass was analyzed for triglyceride content which was found to be 9.3% of the dry biomass. However, when algal cells were left for additional 10 days in static conditions the triglyceride content increased to 28.8%. These data show that this Scenedesmus strain can be used for wastewater bioremediation producing a biomass suitable for energy production.

The Potential of Biodiesel Production from Fatty Acid Methyl Esters of Some European/Mediterranean and Cosmopolitan Halophyte Seed Oils

Abstract Biodiesel fuel, mainly produced from edible vegetable oils, has been proposed as a renewable substitute for petroleum diesel. However, there is growing concern about its role in rising food prices, accelerating deforestation, and displacing existing agricultural production. Moreover, given the progressive shortages of freshwater resources and arable land, a major target of investigations is to evaluate the potential utilization of promising salt-tolerant halophytic non-food crops for the sustainable production of oil-rich biomass, which will be converted to fuel. In this paper, an attempt has been made to look into the potential of the exploitation of native halophytic plants in European and Mediterranean arid or semi-arid lands that can prosper in seawater or brackish waters for diesel production in Europe. Fatty acid (FA) profiles of seed oils of 37 European and Mediterranean halophytic plant species including some of cosmopolitan distribution were examined. The saponification number, iodine value (IV), cetane index (CI), and gross heat of combustion of FA methyl esters (FAMEs) of oils were calculated from reported FAMEs compositions, and they varied from 165.3 to 193.3, from 71.8 to 173.7, from 35.9 to 60.0, and from 39.86 to 40.41 MJ/kg, respectively. FA seed oil content and composition, IV, CI, linolenic acid ME, and polyunsaturated ME (with ≥4 double bonds) contents were used to predict the quality of FAME of oil for use as biodiesel, according to EN 14214 European standard. Crithmum maritimum and Crambe maritima, having more than 30 % fixed oil in their seeds, were found most suitable as alternative vegetable oil sources for the production of biodiesel.