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Conversion of Biodiesel Byproduct Glycerol to Arabitol and Sophorolipids Through Microbial Fermentation

Koganti, Srujana
http://rave.ohiolink.edu/etdc/view?acc_num=akron1334676698

Abstract Details

2012, Doctor of Philosophy, University of Akron, Chemical Engineering.
Biodiesel is an attractive alternative fuel produced by renewable resources and glycerol is a major byproduct in biodiesel production. It is important to find commercial/industrial applications of glycerol for the sustainability and economics of biodiesel industry. We found the use of glycerol in producing the sugar alcohol, arabitol, using Debaryomyces hansenii and the group of biosurfactants, sophorolipids, using Candida bombicola through microbial fermentation. Arabitol, a stereoisomer to xylitol, has the potential applications as a sweetener for diabetic patients and reducer of dental caries. About 217 strains were screened by our project partner, the late Dr. Tsung Min Kuo, at the United States Department of Agriculture for their ability to produce arabitol from glycerol as carbon source. A D. hansenii strain was chosen from the screening process due to its better arabitol production compared to other strains and for being able to produce arabitol as the only polyol. We successfully achieved the optimal conditions that are required for maximum arabitol production from glycerol as a substrate using D. hansenii. The optimal conditions thus found were 5% dissolved oxygen, 3.5 pH, temperature of 30 °C and nitrogen-to-phosphorous ration of 9 to achieve a yield of 55% and a productivity of 0.2 g/L-h. It was found in our study that high glycerol concentrations (at least 100 g/L) are favorable in improving the arabitol yield from 14% to 40% with 50 g/L and 100 g/L initial glycerol concentration respectively. However, higher glycerol concentrations needed longer fermentation run time for complete consumption of glycerol, particularly when the rates of consumption of glycerol and production of arabitol slowed and even stopped as the yeast cells entered into an extended stationary phase. This problem was shown to be solvable by the addition of organic nitrogen source, to reinvigorate the cells, and xylose, as a cosubstrate. This method could not only improve the yield but also the productivity of arabitol from 0.1 g/L-h to 0.5 g/L-h. Such successful method of producing arabitol using glycerol reduces the production costs. One of the ways of reducing the production cost in industrial scale is to use low cost raw materials and in this study it was achieved by the use of biodiesel glycerol. Another potential option found in our study was the potential use of lignocellulose materials as the raw materials for the production of arabitol. The ability of D. hansenii in utilizing glucose, xylose and their representing the lignocellulose hydrolysate was studied and good arabitol production was achieved. Lignocellulose hydrolysate majorly contains mixtures of glucose, xylose, and other sugars in lower amounts. Another use of biodiesel glycerol studied in this research was for the production of sophorolipids. Biosurfactants have many applications in food, cosmetic and drug industries. Sophorolipids are usually produced from a combination of hydrophobic carbon source and lipid precursor. Biodiesel waste product was used for sophorolipids production by others but the specific yield of sophorolipids achieved in our research was higher (2.5 g sophorolipids/ g of cells) which was achieved by the controlled addition of lipid precursor compared to others with 1.5 g sophorolipids/ g cells. Further, optimization studies could be done using biodiesel glycerol to improve the productivity and yield.
Lu-Kwang Ju, Dr. (Advisor)
George Chase, Dr. (Committee Member)
Jie Zheng, Dr. (Committee Member)
Narender Reddy, Dr. (Committee Member)
John Senko, Dr. (Committee Member)
205 p.
Chemical Engineering
Arabitol; Sophorolipids; Biodiesel; Glycerol; Xylitol

Recommended Citations

Citations

  • Koganti, S. (2012). Conversion of Biodiesel Byproduct Glycerol to Arabitol and Sophorolipids Through Microbial Fermentation [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1334676698

    APA Style (7th edition)

  • Koganti, Srujana. Conversion of Biodiesel Byproduct Glycerol to Arabitol and Sophorolipids Through Microbial Fermentation. 2012. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1334676698.

    MLA Style (8th edition)

  • Koganti, Srujana. "Conversion of Biodiesel Byproduct Glycerol to Arabitol and Sophorolipids Through Microbial Fermentation." Doctoral dissertation, University of Akron, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1334676698

    Chicago Manual of Style (17th edition)

akron1334676698
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© 2012, some rights reserved.Creative Commons License Conversion of Biodiesel Byproduct Glycerol to Arabitol and Sophorolipids Through Microbial Fermentation by Srujana Koganti is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by University of Akron and OhioLINK.