Lipid production from indigenous Greek microalgae: a possible biodiesel source.

OBJECTIVE: Microalgae gained interest for potential use as biodiesel producers, since they synthesize and accumulate significant quantities of lipids. The aim of this work was to isolate indigenous microalgae strains from Greek habitats, study their physicochemical growth conditions and finally select the best ones with respect to overall lipid production and profile. RESULTS: Two sampling sites of marine aquatic ecosystems were selected in Attica prefecture, Greece in order to screen for novel wild type strains with lipid production capacity. Microalgae isolates (59) were obtained from the selected areas and were morphologically and molecularly characterized. Fatty acids were estimated through Flow Cytometry combined with BODIPY staining method. Four isolates were selected for their lipid production properties and were cultivated in 15 L tank cultures. The four isolates were also identified by 18S rDNA gene sequencing. Two of them, Chlorella sp. ΑCΑ9 and ACA17, exhibited both maximum biomass and lipid productivity. Optimization of growth conditions with respect to pH and initial NaNO3 concentration was performed for the two microalgae in 15 L cultures. Finally, 20 L fed batch cultures were set up using the optimum culture conditions. Lipid profiles were stabilized for both strains at dry biomass levels over 1 g L-1 and lipid content of 25% (w/w). CONCLUSIONS: Two Chlorella strains (ACA9 and ACA17) were promising candidates for biodiesel production as they were easily grown in sea water in fed batch systems and produce lipids suitable for biodiesel-especially Chlorella sp. ACA9.

Evaluation of Paecilomyces variotii potential in bioethanol production from lignocellulose through consolidated bioprocessing.

The ascomycete Paecillomyces variotii was evaluated for the first time as a candidate species for the production of bioethanol from lignocellulose through consolidated bioprocessing (CBP) approaches. The examined strain (ATHUM 8891) revealed all the necessary phenotypic characteristics required for 2nd generation biofuel production. The fungus is able to efficiently ferment glucose and xylose to ethanol, with yields close to the theoretical maximum. Nitrogen supplementation greatly affected ethanol production with nitrate-nitrogen presenting the best results. Notably, ethanol yield on xylose fermentation was higher than that of glucose, while in co-fermentation of glucose-xylose mixtures no distinguished diauxic behavior was observed. Furthermore, the fungus seems to possess the necessary enzyme factory for the degradation of lignocellulosic biomass, as it was able to grow and produce ethanol on common agro-industrial derivatives. Overall, the results of our study indicate that P. variotii is a new and possibly powerful candidate for CBP applications.

Unraveling the lipolytic activity of thermophilic bacteria isolated from a volcanic environment.

In a bioprospecting effort towards novel thermostable lipases, we assessed the lipolytic profile of 101 bacterial strains isolated from the volcanic area of Santorini, Aegean Sea, Greece. Screening of lipase activity was performed both in agar plates and liquid cultures using olive oil as carbon source. Significant differences were observed between the two screening methods with no clear correlation between them. While the percentage of lipase producing strains identified in agar plates was only 17%, lipolytic activity in liquid culture supernatants was detected for 74% of them. Nine strains exhibiting elevated extracellular lipase activities were selected for lipase production and biochemical characterization. The majority of lipase producers revealed high phylogenetic similarity with Geobacillus species and related genera, whilst one of them was identified as Aneurinibacillus sp. Lipase biosynthesis strongly depended on the carbon source that supplemented the culture medium. Olive oil induced lipase production in all strains, but maximum enzyme yields for some of the strains were also obtained with Tween-80, mineral oil, and glycerol. Partially purified lipases revealed optimal activity at 70-80°C and pH 8-9. Extensive thermal stability studies revealed marked thermostability for the majority of the lipases as well as a two-step thermal deactivation pattern.