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The discharge of palm oil mill effluent (POME) on arable land causes large amounts of environmental distress due to its high concentration of phenolic compounds and chemical oxygen demand (COD). The approach of simultaneous microbial oil production and wastewater treatment is an attractive option to combine renewable energy production and environmental resilience. This study aims to produce cost effective microbial lipids using the oleaginous yeast Lipomyces starkeyi through the bioremediation of POME. A moderately dilute solution (50%) of POME showed higher microbial growth and lipid accumulation and offered a significantly higher degree of bioremediation. A lipid content of 21.32% was achieved with 50% POME, whereas the value was 15.14% for 25% POME. Three different techniques including ultrasonic treatment, Fenton's reagent and Fenton's + ultrasonic were employed to extract lipids from microbial biomass, and the maximum lipid concentration was obtained using the Fenton's + ultrasonic treatment. The degree of bioremediation was evaluated by the calculating seed germination index (GI) values. Higher GI values were observed for the 25% and 50% dilutions compared to undiluted (100%) POME. This combined approach can be a potential alternative technology that integrates bioremediation of POME with microbial lipid production. [ABSTRACT FROM AUTHOR]

In this study, the oleaginous yeasts cultured in tomato waste hydrolysates (TWH) to produce microbial lipids that offer a suitable alternative to vegetable oils as feedstock for the biodiesel synthesis. The TWH were prepared by acid hydrolysis (2.5% H2SO4). To obtain higher growth rates, as well as higher lipid contents, Lipomyces starkeyi were cultured under original nitrogen content (TWHON), lower nitrogen content (TWHLN), attained by alkaline precipitation of TWHON followed by centrifugation and filtration, and higher nitrogen content (TWHHN), prepared by addition of (NH4)2SO4. To reduce the effect of the inhibitors of the microbial growth (acetic acid, furfural etc.) generated during the acid hydrolysis of tomato waste, the hydrolysates were preliminary diluted. However, the highest values of microbial growth and biomass yield were observed when using undiluted medium with lower nitrogen content. The addition of a N source to the medium had no significant effect on the growth rate of the yeasts, as well as on lipid accumulation. The distribution of fatty acids in microbial lipids was almost similar to that of plant oils. Consequently, these lipids can be used to synthesize a biodiesel offering excellent performances as automotive fuel. [ABSTRACT FROM AUTHOR]

Abstract: Biodiesel can be a potential alternative to petroleum diesel, but its high production cost has impeded its commercialization in most parts of the world. One of the main drivers for the generation and use of biodiesel is energy security, because this fuel can be produced from locally available resources, thereby reducing the dependence on imported oil. Many countries are now trying to produce biodiesel from plant or vegetable oils. However, the consumption of large amounts of vegetable oils for biodiesel production could result in a shortage in edible oils and cause food prices to soar. Alternatively, the use of animal fat, used frying oils, and waste oils from restaurants as feedstock could be a good strategy to reduce the cost. However, these limited resources might not meet the increasing demand for clean, renewable fuels. Therefore, recent research has been focused the use of residual materials as renewable feedstock in order to lower the cost of producing biodiesel. Microbial oils or single cell oils (SCOs), produced by oleaginous microorganisms have been studied as promising alternatives to vegetable or seed oils. Various types of agro-industrial residues have been suggested as prospective nutritional sources for microbial cultures. Since the most abundant residue from agricultural crops is lignocellulosic biomass (LCB), this byproduct has been given top-priority consideration as a source of biomass for producing biodiesel. But the biological transformation of lignocellulosic materials is complicated due to their crystalline structure. So, pretreatment is required before they can be converted into fermentable sugar. This article compares and scrutinizes the extent to which various microbes can accumulate high levels of lipids as functions of the starting materials and the fermentation conditions. Also, the obstacles associated with the use of LCB are described, along with a potentially viable approach for overcoming the obstacles that currently preclude the commercial production of biodiesel from agricultural biomass. [Copyright &y& Elsevier]

Microbial lipids are considered as a promising and sustainable feedstock for biodiesel production due to their fatty acid composition similar to that of vegetable oils. So far, microalgae have attracted more attention as a lipid producer in comparison to other non-photosynthetic oleaginous microbes. Nevertheless, recent studies showed the efficiency of other microorganisms, including bacteria, yeasts, molds which are able to accumulate lipids over 20 % of their dry biomass. Competence of lipid production by those photosynthetic and non-photosynthetic microbes are highly depend on the cost of reactor design, wide range of nutritional substrates, scalability, parasitic energy demand, metabolic function etc. Therefore, integration of biology and engineering is essential for a cost-effective production of microbial lipids. This paper compares microalgae and non-photosynthetic microbes as regards the factors affecting the techno-economical feasibility of the microbial oil production [ABSTRACT FROM AUTHOR]

Hydrolysates of Giant reed ( Arundo donax ) biomass from three different agronomical conditions were used to grow the oleaginous yeast L. Starkey . The agronomical conditions affected the cellulose fraction of biomass, the amount of inhibitors generated during the acid hydrolysis, and the triglyceride yield after the yeast fermentation. Yet, the composition of triglycerides was not affected. Different approaches were developed to reduce the effect of inhibitors. The preliminary dilution of hydrolysates was studied, obtaining the highest values of biomass and lipid yields with a 50% dilution. Alternatively, the hydrolysates were pre-treated by adsorption and overliming. The latter pre-treatment gave the best results. A third approach was offered by the use of pre-adapted yeasts, that were able to grow in the presence of raw hydrolysates. The composition of the microbial triglycerides was compatible with the production of a biodiesel suitable for use as automotive fuel. [ABSTRACT FROM AUTHOR]

Highlights: [•] Catalyst CuO/C was prepared by a novel technique where activated carbon was introduced with nano-sol. [•] The free fatty acid conversion was achieved up to 95% using 8wt% catalysts. [•] High catalytic activity was observed and activity was lost about 20% after four cycles uses. [Copyright &y& Elsevier]