Olive mill wastewater as a renewable resource

The olive mill wastewater (OMW) is a stable emulsion composed by water, olive pulp and residual oil. An approach for using this waste as a renewable resource is of greater interest. Several authors have been studding physicochemical treatment methods. However, the biological treatments allow not only the treatment, but also the effluent valorization, by producing several valuable products. This effluent is also a source of natural antioxidants and its extraction is economically attractive. The ideal OMW valorization process could be achieved by the combination of methods, for instance the use of physical-chemical methods as pretreatment can highly reduce the pollutants concentrations and allows better production efficiency by microorganisms

Dissolved oxygen effect on microbial lipids production by Yarrowia lipolytica from volatile fatty acids

Volatile fatty acids (VFAs) can be obtained from organic wastes through acidogenic fermentation and the yeast Yarrowia lipolytica can use those VFAs for the biosynthesis of lipids. Oxygen is an important factor of the bioconversion process of VFAs into microbial lipids by Y. lipolytica, thus the effect of oxygenation was evaluated in batch cultures of the yeast for two different strains, varying the stirring and air flow rates. The increase of dissolved oxygen concentration improved lipid production by Y. lipolytica W29 and Y. lipolytica NCYC 2904 in glucose and VFAs (acetate, propionate and butyrate) medium. The strain NCYC 2904 accumulated higher intracellular lipids (22%, w/w) than strain W29 (12%, w/w) with differences in lipids composition. Lipids of strain W29 were mainly composed by linoleic acid (up to 47%) and oleic acid (up to 31%) and NCYC 2904 accumulated predominantly oleic acid (around 56%). For both strains, the unsaturated fraction (> 70%) exceeded the saturated one. Since fatty acid composition in Y. lipolytica are similar to common vegetable oils (usually used for biodiesel production), these lipids are a potential feedstock for biofuels production.Projects TUBITAK/0009/2014; UID/BIO/04469/2019, grant SFRH/BD/129592/2017. BioTecNorte (NORTE-01-0145-FEDER000004).info:eu-repo/semantics/publishedVersio

Bioconversion of volatile fatty acids into microbial lipids by Yarrowia lipolytica

Volatile fatty acids (VFAs) are short chain fatty acids that can be obtained from organic wastes through acidogenic fermentation and can be used as carbon source for microbial lipids production. The bioconversion of acetate, propionate and butyrate into microbial lipids by Yarrowia lipolytica W29 was evaluated, and the yeast shown the ability to grow using VFA as carbon source and accumulate lipids intracellularly (around 5 % of dry cell mass). The addition of a co-substrate (glucose or glycerol) to VFA-based medium led to an enhancement of cellular growth and lipid content of the cells. The highest lipids concentration of around 1 g/L was obtained in batch cultures carried out with a mixture of VFAs and glycerol. Notwithstanding the low lipid content obtained in this work, Y. lipolytica demonstrated the ability to metabolize VFAs and convert them to microbial lipids, which can be used for biodiesel production.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the project TÜBITAK 2014 (TUBITAK/0009/2014) and of the strategic funding of UID/BIO/04469 unit and COMPETE 2020 (POCI-01-0145-FEDER006684), Post-Doctoral grant (SFRH/BPD/101034/2014), Doctoral grant (SFRH/BD/129592/2017) and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte.info:eu-repo/semantics/publishedVersio

Yarrowia lipolytica is a promising oleaginous yeast for bio-oils production from volatile fatty acids

Every year, approximately 931 million tons of food waste (FW) are generated worldwide. The discharge of FW in the landfill has a negative environmental impact due to water and soil pollution and GHG emission. Volatile fatty acids (VFAs), produced by anaerobic fermentation of FW, can be used as a substrate by oleaginous yeasts to produce bio-oils. The bioconversion of pure VFAs into Y. lipolytica biomass and bio-oils was affected by oxygenation conditions in batch cultures carried out in a stirred-tank bioreactor. Approximately 3-fold enhancement in lipids concentration was obtained by increasing the agitation and aeration rates. Two-stage batch cultures (1st stage growth in glucose; 2nd stage bio-oils production in VFAs) proved to be an effective approach to improve lipids accumulation from pure VFAs. The highest lipid content was attained in conditions of dissolved oxygen concentration of 45% of saturation during the lipogenic phase. Y. lipolytica also accumulated lipids in food waste-derived VFAs, particularly in two-stage batch cultures (1st stage growth in VFAs; 2nd stage bio-oils production in crude glycerol). These bio-oils are promising feedstock for the biodiesel industry and the estimated fuel properties of biodiesel are in accordance with international standards.info:eu-repo/semantics/publishedVersio

Vince – a case study

Vince was an unusual hurricane that developed over the North Atlantic Ocean in an unexpected area, on October 2005. In this work, the authors analyze its background and genesis over the ocean, making use of satellite imagery and numerical models. The impacts on sea state are investigated both numerically and observationally. Landfall over the Iberian Peninsula is monitored with surface observations and a radar system at Algarve (Portugal)

Hydrogenotrophic activity under increased H₂/CO₂ pressure: effect on methane production and microbial community

H2 and CO2 are main compounds of synthesis gas. Efficient conversion of syngas to biomethane is a straightforward strategy to integrate the energy value of syngas into existing natural gas grid infrastructures. In this study, the effect of initial H2/CO2 (80/20, v/v) pressure on methane production rate and microbial community diversity was assessed in a hyperbaric bioreactor inoculated with anaerobic granular sludge. Several batch experiments were performed to distinguish between the effect of initial total gas pressure and H2/CO2 partial pressure: (1) varying initial gas pressure (from 1 to 6 bar) with 100% H2/CO2 mixture; (2) constant initial gas pressure (5 bar), with increasing H2/CO2 partial pressure (from 1 to 5 bar); (3) varying initial gas pressure (from 2 to 5 bar) with constant H2/CO2 partial pressure (2 bar). In (2) and (3), N2 was used for ensuring the necessary overpressure. Microbial community changes in the system were monitored by 16S rRNA-based techniques (PCR-DGGE). The raise of H2/CO2 initial pressure (100% H2/CO2) from 1 to 5 bar led to an improvement in methane rate production from 0.035 ± 0.014 mmol h1 to 0.072 ± 0.019 mmol h1. Similar methane production rates were observed in reactors operated at the same H2/CO2 partial pressures, even when varying the total initial gas pressure. Hydrogen partial pressure was shown to determine the structure of bacterial communities and diversity decreased with increasing H2/CO2 partial pressure. No significant changes were observed for the archaeal communities

Pressurized syngas bioconversion: physiological and microbial characterization

ICBM-3 - 3rd International Conference on Biogas MicrobiologySyngas is composed mainly by CO, H2 and CO2 and its fermentation is a promising biological process to produce fuels or commodity chemicals. Experiments under increased initial syngas pressures, up to 5.2×105 Pa, were carried out to evaluate the effects on metabolites production and microbial communities structure. Two strategies were applied: NB non-adapted biomass and SB successively syngas-fed biomass. The rise of syngas pressure from 1.2×105 Pa up to 5.2×105 Pa led to a decrease on CO and H2 consumption rates and CH4 production rate. Moreover, when methanogenesis was partially inhibited, propionate and butyrate were the main metabolites produced from syngas. DGGE profiles showed differences on diversity and on similarity indices (SI) with changes in pressure. Regardless the syngas pressure employed, the archaeal communities had higher SI (above 70%) than bacterial community (48% to 62%). From the Illumina sequencing analysis, it was observed that the relative abundance of bacterial communities tend to decrease (72% to 46%), and archaeal communities increased (25% to 54%) by raising the pressure of syngas from 1.2×105 Pa to 5.2×105 Pa. In the inoculum and biomass incubated at 1.2×105 Pa syngas, 40% of total population were from Proteobacteria phylum and Deltraproteobacteria class and their abundance was reduced 4-fold at 5.2×105 Pa. As a direct effect of high pressures of syngas, organisms belonging to Firmicutes, Synergistetes and Thermotogae phyla increased over 10-fold. The predominant phylotypes at 3×105 Pa and 5.2×105 Pa were related to Methanobacterium genus (archaea) and to Eubacteriaceae, Synergistaceae and Syntrophobacteraceae families (bacteria). These results showed a microbial population enrichment suggesting a high specialization for the substrate.info:eu-repo/semantics/publishedVersio