Biodiesel production from lignocellulosic biomass using Yarrowia lipolytica.

What is it about?

Depletion of hydrocarbons is forcing to find alternative resources to meet the energy demand of the growing population. Microbial biodiesel as a fuel can act as a cheaper and eco-friendly alternative to fossil fuel. Single-cell oil (SCO) consisting of carbon, hydrogen and oxygen grown over the lignocellulosic biomass using oleaginous microorganisms are triacylglycerols which can be converted to biodiesel, with physicochemical properties similar to conventional diesel. However, several cost-effective pretreatment methods are required to utilize lignocellulosic biomasses. The current research study investigates the SCO yield (and biodiesel characteristics) obtained from sugarcane bagasse hydrolysate through various pretreatment techniques. The pretreatment with 4% v/v H2SO4 at 25 min of ultra-sonication provided the best depolymerisation results (based on the glucose concentration). Yarrowia lipolytica was inoculated into the hydrolysates, allowed to grow at 25 °C, pH of 6.5 and rapid mixing for six days yielded biomass of 16.39 g/l. Biodiesel was extracted from the biomass via in-situ and ex-situ transesterification. In-situ transesterification carried out with the catalyst K2CO3 yields 80% biodiesel. In comparison, 63% were achieved with ex-situ transesterification, where lipid extraction was carried out as a first step and Tran esterified further in the presence of catalyst KOH to obtain biodiesel. The obtained fatty acid methyl esters (FAME) was subjected to FTIR analysis, and the observed physicochemical properties were within the international standards.

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Why is it important?

The economic development (due to the unprecedented utilization of fossil fuels) was attained at the cost of environmental concerns such as global warming, ozone layer depletion, climate change, melting of polar glaciers and defforestation [1]. The present era was confronted with many concerns of population explosion and energy crisis due to depleting fossil fuel reserves resulting in substantial crude oil production. These issues could be partly addressed by exploring non-conventional energy sources [2]. This critical situation warrants the demand for alternative fuels and in the coming decades is expected to have more contribution from biofuels rather than the fossil fuel sector [3], [4], [5]. Biodiesel is a potential sustainable fuel made from plant, animal, and microbial lipids with oleaginous ability. To meet the high demand of fuel, interest in 3rd generation biodiesel produced from oleaginous microorganisms (OM) has grown significantly [6], [7]. Using OMs may also help realise the circular economy and create cost-effective procedures. For example, biodiesel produced from waste product crude glycerol may be used as a carbon source for lipid build-up [8]. These lipids may then be regenerated into fatty acid methyl esters (FAMEs) and glycerol. Adopting to this procedure may result in cost-effective biodiesel synthesis from agro-residues, glycerol, and other waste substrates [9]. It is irrational to depend on the edible feedstock (as raw materials) for biodiesel production because a huge population relies on edible vegetable oil that accounts for a production rate of nearly 30 billion tons per year [10].

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