Construction of a whole-cell catalyst displaying a fungal lipase for effective treatment of oily wastewaters

Effect of carbon source on lipid accumulation and biodiesel production of Yarrowia lipolytica

Yarrowia lipolytica (Y. lipolytica) is an oleaginous yeast that can utilize hydrophobic substrates as carbon source to produce single-cell lipids for biodiesel production. This study attempts to increase the lipid accumulation ability of Y. lipolytica by first gradually elevating pure oil substrate concentration during the cultivation and then adding short-chain carbon compounds, such as glucose and sodium acetate, to a culture substance according to the optimal oil concentration. Results showed that Y. lipolytica cultured under 40.0 g L^-1 oil concentration showed higher lipids (2.97 g L^-1) and lipid content (37.35%, DW) compared with that cultured under 20.0 g L^-1, where the corresponding values were 1.91 g L^-1 and 24.46%. By contrast, the lipid content of Y. lipolytica increased from 37.35 to 41.50% when the substrate was changed from 40.0 g L^-1 pure oil to 5% sodium acetate combined with 95% oil under the same total carbon concentration. However, lipid accumulation did not increase even though 15% sodium acetate or 5% glucose, or 15% glucose was added to the combined substrate. Moreover, the lipid biomodification of Y. lipolytica was evident when it was cultured under the oil concentration of 20.0 g L^-1. Therefore, the lipid accumulation of Y. lipolytica can be elevated through the gradient increase of oil concentration and by adding a suitable amount of easily degradable carbon source. Furthermore, the lipid biomodification of Y. lipolytica improves biodiesel quality.

Novel fabrication of a robust superhydrophobic PU@ZnO@Fe3O4@SA sponge and its application in oil-water separations

We report a novel superhydrophobic material based on commercially available polyurethane (PU) sponge with high porosity, low density and good elasticity. The fabrication of a superhydrophobic sponge capable of efficiently separating oil from water was achieved by imitating or mimicking nature's designs. The original PU sponge was coated with zinc oxide (ZnO), stearic acid (SA) and iron oxide particles (Fe3O4) via a facile and environmentally friendly method. After each treatment, the properties of the modified sponge were characterized, and the changes in wettability were examined. Water contact angle (WCA) measurements confirmed the excellent superhydrophobicity of the material withhigh static WCA of 161° andlow dynamic WCA (sliding WCA of 7° and shedding WCA of 8°). The fabricated sponge showed high efficiency in separation (over 99%) of different oils from water. Additionally, the fabricated PU@ZnO@Fe3O4@SA sponge could be magnetically guided to quickly absorb oil floating on the water surface. Moreover, the fabricated sponge showed excellent stability and reusability in terms of superhydrophobicity and oil absorption capacity. The durable, magnetic and superhydrophobic properties of the fabricated sponge render it applicable to the cleanup of marine oil spills and other oil-water separation issues, with eco-friendly recovery of the oil by simple squeezing process.

Recent improvements in oily wastewater treatment: Progress, challenges, and future opportunities

Oily wastewater poses significant threats to the soil, water, air and human beings because of the hazardous nature of its oil contents. The objective of this review paper is to highlight the current and recently developed methods for oily wastewater treatment through which contaminants such as oil, fats, grease, and inorganics can be removed for safe applications. These include electrochemical treatment, membrane filtration, biological treatment, hybrid technologies, use of biosurfactants, treatment via vacuum ultraviolet radiation, and destabilization of emulsions through the use of zeolites and other natural minerals. This review encompasses innovative and novel approaches to oily wastewater treatment and provides scientific background for future work that will be aimed at reducing the adverse impact of the discharge of oily wastewater into the environment. The current challenges affecting the optimal performance of oily wastewater treatment methods and opportunities for future research development in this field are also discussed.

Pretreatment of coconut mill effluent using celite-immobilized hydrolytic enzyme preparation from Staphylococcus pasteuri and its impact on anaerobic digestion

Biological treatment of oil and grease (O&G)-containing industrial effluents has long been a challenging issue. Practically feasible avenues to bring down their O&G load and enhance treatability are desired. In one such endeavour, the partially purified lipase from Staphylococcus pasteuri COM-4A was immobilized on celite carrier and applied for the enzymatic hydrolysis of unsterilized coconut oil mill effluent. In batch hydrolysis experiments, optimum conditions of 1% (w/v) immobilized lipase beads, one in four effluent dilution, and a contact time of 30 h resulted in 46% and 24% increase in volatile fatty acids and long-chain fatty acids and a concomitant 52% and 32% decrease in O&G and chemical oxygen demand (COD) levels, respectively. Batch anaerobic biodegradation trials with this prehydrolyzed effluent showed 89%, 91%, and 90% decrease in COD, proteins, and reducing sugars, respectively. These results were validated in a hybrid stirred tank--upflow anaerobic sludge blanket reactor. Average COD and O&G reductions effected by the hybrid reactor were found to be 89% and 88%, whereas that by the control reactor without enzymatic hydrolysis were only 60% and 47%, respectively. A maximum of 0.86 L methane gas was generated by the hybrid reactor per gram of VS added. Hence, this celite-immobilized crude lipase, sourced from a native laboratory isolate, seems to be a workable alternative to commercial enzyme preparations for the management of lipid-rich industrial effluents.

Yarrowia lipolytica: recent achievements in heterologous protein expression and pathway engineering

The oleaginous yeast Yarrowia lipolytica has become a recognized system for expression/secretion of heterologous proteins. This non-conventional yeast is currently being developed as a workhorse for biotechnology by several research groups throughout the world, especially for single-cell oil production, whole cell bioconversion and upgrading of industrial wastes. This mini-review presents established tools for protein expression in Y. lipolytica and highlights novel developments in the areas of promoter design, surface display, and host strain or metabolic pathway engineering. An overview of the industrial and commercial biotechnological applications of Y. lipolytica is also presented.

Oily wastewaters treatment using Pseudomonas sp. isolated from the compost fertilizer

BACKGROUND

Discharging the oily wastewater in the environment causes serious problems, because of the oil compounds and organic materials presence. Applying biological methods using the lipase enzyme producer microorganisms can be an appropriate choice for treatment of these wastewaters. The aim of this study is to treat those oil wastewaters having high concentration of oil by applying lipase enzyme producer bacteria.

MATERIALS AND METHODS

Oil concentration measurement was conducted using the standard method of gravimetric and the wastewater under study was synthetically made and contained olive, canola and sunflower oil. The strain used in this study was Pseudomonas strain isolated from compost fertilizer. The oil under study had concentration of 1.5 to 22 g/l.

RESULTS

The oil removal amount in concentrations lower than 8.4 g/l was over 95 ± 1.5%. Increase of the oil's concentration to 22 g/l decreases the amount of removal in retention time of 44 hours to 85 ± 2.5%. The best yield of removing this strain in retention time of 44 hours and temperature of 30°C was achieved using Ammonium Nitrate as the nitrogen resource which yield was about 95 percent.

CONCLUSION

The findings of the research showed that Pseudomonas bacteria isolated from the compost fertilizer can degrade high concentration oils.

Yarrowia lipolytica and pollutants: Interactions and applications

Yarrowia lipolytica is a dimorphic, non-pathogenic, ascomycetous yeast species with distinctive physiological features and biochemical characteristics that are significant in environment-related matters. Strains naturally present in soils, sea water, sediments and waste waters have inherent abilities to degrade hydrocarbons such as alkanes (short and medium chain) and aromatic compounds (biphenyl and dibenzofuran). With the application of slow release fertilizers, design of immobilization techniques and development of microbial consortia, scale-up studies and in situ applications have been possible. In general, hydrocarbon uptake in this yeast is mediated by attachment to large droplets (via hydrophobic cell surfaces) or is aided by surfactants and emulsifiers. Subsequently, the internalized hydrocarbons are degraded by relevant enzymes innately present in the yeast. Some wild-type or recombinant strains also detoxify nitroaromatic (2,4,6-trinitrotoluene), halogenated (chlorinated and brominated hydrocarbons) and organophosphate (methyl parathion) compounds. The yeast can tolerate some metals and detoxify them via different biomolecules. The biomass (unmodified, in combination with sludge, magnetically-modified and in the biofilm form) has been employed in the biosorption of hexavalent chromium ions from aqueous solutions. Yeast cells have also been applied in protocols related to nanoparticle synthesis. The treatment of oily and solid wastes with this yeast reduces chemical oxygen demand or value-added products (single cell oil, single cell protein, surfactants, organic acids and polyalcohols) are obtained. On account of all these features, the microorganism has established a place for itself and is of considerable value in environment-related applications.

Food-related applications of Yarrowia lipolytica

Yarrowia lipolytica is a non-pathogenic generally regarded as safe yeast. It displays unique physiological as well as biochemical properties that are relevant in food-related applications. Strains naturally associated with meat and dairy products contribute towards specific textures and flavours. On some occasions they cause food spoilage. They produce food-additives such as aroma compounds, organic acids, polyalcohols, emulsifiers and surfactants. The yeast biomass has been projected as single cell oil and single cell protein. Y. lipolytica degrades or upgrades different types of food wastes and in some cases, value-added products have also been obtained. The yeast is thus involved in the manufacture of food stuffs, making of food ingredients, generation of biomass that can be used as food or feed and in the effective treatment of food wastes. On account of all these features, this versatile yeast is of considerable significance in food-related applications.

Yarrowia lipolytica: safety assessment of an oleaginous yeast with a great industrial potential

Yarrowia lipolytica has been developed as a production host for a large variety of biotechnological applications. Efficacy and safety studies have demonstrated the safe use of Yarrowia-derived products containing significant proportions of Yarrowia biomass (as for DuPont's eicosapentaenoic acid-rich oil) or with the yeast itself as the final product (as for British Petroleum's single-cell protein product). The natural occurrence of the species in food, particularly cheese, other dairy products and meat, is a further argument supporting its safety. The species causes rare opportunistic infections in severely immunocompromised or otherwise seriously ill people with other underlying diseases or conditions. The infections can be treated effectively by the use of regular antifungal drugs, and in some cases even disappeared spontaneously. Based on our assessment, we conclude that Y. lipolytica is a "safe-to-use" organism.