Abstract
Lipids from oleaginous microorganisms, including oleaginous yeasts, are recognized as feedstock for biodiesel production. A production process development of these organisms is necessary to bring lipid feedstock production up to the industrial scale. This study aimed to enhance lipid production of low-cost substrates, namely sugarcane top and biodiesel-derived crude glycerol, by using a two-stage cultivation process with Rhodosporidiobolus fluvialis DMKU-SP314. In the first stage, sugarcane top hydrolysate was used for cell propagation, and in the second stage, cells were suspended in a crude glycerol solution for lipid production. Optimization for high cell mass production in the first stage, and for high lipid production in the second stage, were performed separately using a one-factor-at-a-time methodology together with response surface methodology. Under optimum conditions in the first stage (sugarcane top hydrolysate broth containing; 43.18 g/L total reducing sugars, 2.58 g/L soy bean powder, 0.94 g/L (NH4)2SO4, 0.39 g/L KH2PO4 and 2.5 g/L MgSO4 7H2O, pH 6, 200 rpm, 28 °C and 48 h) and second stage (81.54 g/L crude glycerol, pH 5, 180 rpm, 27 °C and 196 h), a high lipid concentration of 15.85 g/L, a high cell mass of 21.07 g/L and a high lipid content of 73.04% dry cell mass were obtained.
Highlights
Biodiesel has largely been accepted as an alternative energy source to fossil fuel, as it is renewable and less toxic
The R. fluvialis DMKU-SP314 used in this study was reported to accumulate a high lipid content (55% of dry cell mass) in nitrogen-limited medium II containing a 70 Glycerol concentration (g/L) mixture of glucose and xylose in a ratio of 2:1 by shaking flask cultivation at 150 rpm and 28 ◦C for 240 h, and, in an optimized lipid production medium for shaking flask cultivation containing sugarcane top hydrolysate (STH) supplemented with 59 g/L Crude glycerol (CG), 66.6% of dry cell mass was obtained [29]
The results showed that the optimal conditions for lipid production with R. fluvialis DMKU-SP314 corresponded to 87.54 g/L CG with an initial pH of 5 and a shaking speed of 180 rpm
Summary
Biodiesel has largely been accepted as an alternative energy source to fossil fuel, as it is renewable and less toxic. The most recent generation of biodiesel is derived from microbial lipids. Using recovered animal fats and frying oils of the second generation as feedstock for biodiesel can efficiently reduce the price of the fuel; the amount of these fats and oils is limited on an industrial scale and cannot meet the increasing needs of biodiesel production [4]. Microbial lipids that are produced by oleaginous microorganisms have been getting increased attention as an oil feedstock [5]. In terms of obtainability and sustainability, lipids from oleaginous microorganisms are recognized as opportunity feedstocks for biodiesel production and provide a promising route to food and energy security in the current energy crisis [6]
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