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Study on Microbial Oil Production by Fermentation of Lignocellulose Hydrolyzate

Author: PengFeng
Tutor: LiuDeHua；LiuCanMing
School: Hunan Agricultural University
Course: Applied Chemistry
Keywords: Lignocellulosic biomass Acid hydrolysis Activated charcoal detoxification Microbial oil Biodiesel
CLC: TQ645
Type: Master's thesis
Year: 2009
Downloads: 160
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Abstract


Energy shortage and environmental pollutions has made the development of renewable energy attract much interest all over the world. One of the promising renewable energy is biodiesel, which has become more attractive recently because of its environmental benefits and the fact that it can be made from renewable resources. Recently, biodiesel is generally prepared by transesterification of plant oil with methanol. However the shortage of raw feedstock has become a bottle-neck for large-scale production of biodiesel. One promises pathway to dissolve this problem could be the exploitation of carbohydrate-based microbial oil. Microbial oils, also referred to as Single Cell Oils (SCO), is produced by some oleaginous microorganisms which can convert renewable material, such as carbohydrates into microbial oils. There are many advantages for microbial oil production, such as rapid growth and short life cycle of microbes, independence of seasons, climates and places, inexpensive biomass substrates and ease of scaling up. Therefore production of microbial oil from low-price carbon source has been thought as a promising approach to produce raw feedstock for biodiesel development in the future.In this thesis, one of the most important lignocellulosic biomass, sugarcane bagasse was hydrolized with dilute acid to obtain fermentable sugars. The hydrolyzate was then detoxified in order to remove the compounds inhibiting the growth of Rhodosporidium toruloides. The effects of seveal factors affeting acid hydrolysis was investigated. Several compounds were added solely or together to the medium to study their inhibitions on the strain growth and sugar consumptions in order to obtain some data for subsequent detoxification process. It was found that when the compound was present solely in the medium, in order to obtain a high cell biomass accumulation, the concentration of formic acid, acetic acid, furfural and vanillin should be lower than 4 g L-1,10 g L-1,1 g L-1 and 1 g L-1, respectively. However, the synergistic effects of these compounds could dramatically decrease their concentrations that displayed significant inhibitions. Further more, the effects of several factors on activated charcoal detoxification of sugarcane bagasse hydrolyzate were investigated and the conditions of detoxification were optimized by response surface methodology (central composite design, CCD). It was found that when the hydrolyzate were detoxified with 3% activated charcoal (w/w) at 80℃and pH 2.0 for 50 min, more than 90% of the lignin decomposition products were removed. Being neutralized by Ca(OH)2, the detoxified hydrolyzate was further used as carbon source for yeast lipids fermentation under nitrogen-limited conditions by Rhodosporidium toruloides AS 2.1389. It was observed that the detoxified hydrolyzate could be well utilized by the yeast to synthesize biomass, and the lipids content reached to 32.99%(w/w) based on dry cell weight, with lipid yield of 12.48 g lipid/l00g sugar.

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CLC: > Industrial Technology > Chemical Industry > Chemical processing of oils and waxes industry, soap industry > Grease industrial products and by-products
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