Title: Presence of glucose, xylose, and glycerol fermenting bacteria in the deep biosphere of the former Homestake gold mine, South Dakota Authors
|Rastogi, Gurdeep -|
|Gurram, Raghu -|
|Bhalla, Aditya -|
|Gonzalez, Ramon -|
|Kumar, Sudhir -|
|Sani, Rajesh -|
Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 26, 2013
Publication Date: February 15, 2013
Citation: Rastogi, G., Gurram, R.N., Bhalla, A., Gonzalez, R., Bischoff, K.M., Hughes, S.R., Kumar, S., Sani, R.K. 2013. Presence of glucose, xylose, and glycerol fermenting bacteria in the deep biosphere of the former Homestake gold mine, South Dakota. Frontiers in Microbiology. 4(2):1-8. Interpretive Summary: In this research, we discovered seven new bacterial strains that could convert sugars or glycerol to valuable fuels and chemicals. Improved microbial strains are needed to convert the mixed sugars derived from agricultural residues into fuels and chemicals. Ethanol was the major product produced by four of the strains grown on the sugars glucose or xylose, while the chemical 1,3-propanediol was the major product from three strains grown on glycerol. These strains have potential industrial application in bio-based refineries that produce value-added bioproducts from agricultural commodities.
Technical Abstract: Eight fermentative bacterial strains were isolated from mixed enrichment cultures of a composite soil sample collected at 1.34 km depth from the former Homestake gold mine in Lead, SD, USA. Phylogenetic analysis of their 16S rRNA gene sequences revealed that these isolates were affiliated with the phylum Firmicutes belonging to genera Bacillus and Clostridium. Batch fermentation studies on selected seven bacterial strains demonstrated that these have the ability to ferment glucose, xylose, or glycerol to industrially valuable products such as ethanol and 1,3-propanediol (PDO). Ethanol was detected as the major fermentation end product in glucose-fermenting cultures at pH 10 with yields of 0.206-0.304 g of ethanol/g of glucose. While a xylose fermenting strain yielded 0.189 g of ethanol/g of xylose and 0.585 g of acetic acid/g of xylose at the end of fermentation. At pH 7, glycerol-fermenting isolates produced PDO (0.323- 0.458 g of PDO/g of glycerol) and ethanol (0.284-0.350 g of ethanol/g of glycerol) as major end products while acetic acid and succinic acid were identified as minor by-products in fermentation broths. These results suggest that these deep-mine bacterial strains could be used in bio-based production of ethanol and PDO, and would have a positive effect on the overall economy of biofuels production processes.