Selective suppression of bacterial contaminants by process conditions during lignocellulose based yeast fermentations

Biotechnology for Biofuels

Eva Albers¹  Emma Johansson²  Carl Johan Franzén¹  Christer Larsson¹ 

[1] Department Chemical and Biological Engineering, Chalmers University of Technology, 412 96 Gothenburg, Sweden

[2] Processum Biorefinery Initiative, 891 80 Örnsköldsvik, Sweden

关键词: Saccharomyces;    yeast;    lignocellulosic;    bacteria;    contaminants;    fermentation;    ethanol;   

Others  :  798360
DOI  :  10.1186/1754-6834-4-59

 received in 2011-10-07, accepted in 2011-12-20,  发布年份 2011

【 摘 要 】

Background

Contamination of bacteria in large-scale yeast fermentations is a serious problem and a threat to the development of successful biofuel production plants. Huge research efforts have been spent in order to solve this problem, but additional ways must still be found to keep bacterial contaminants from thriving in these environments. The aim of this project was to develop process conditions that would inhibit bacterial growth while giving yeast a competitive advantage.

Results

Lactic acid bacteria are usually considered to be the most common contaminants in industrial yeast fermentations. Our observations support this view but also suggest that acetic acid bacteria, although not so numerous, could be a much more problematic obstacle to overcome. Acetic acid bacteria showed a capacity to drastically reduce the viability of yeast. In addition, they consumed the previously formed ethanol. Lactic acid bacteria did not show this detrimental effect on yeast viability. It was possible to combat both types of bacteria by a combined addition of NaCl and ethanol to the wood hydrolysate medium used. As a result of NaCl + ethanol additions the amount of viable bacteria decreased and yeast viability was enhanced concomitantly with an increase in ethanol concentration. The successful result obtained via addition of NaCl and ethanol was also confirmed in a real industrial ethanol production plant with its natural inherent yeast/bacterial community.

Conclusions

It is possible to reduce the number of bacteria and offer a selective advantage to yeast by a combined addition of NaCl and ethanol when cultivated in lignocellulosic medium such as wood hydrolysate. However, for optimal results, the concentrations of NaCl + ethanol must be adjusted to suit the challenges offered by each hydrolysate.

【 授权许可】

   
2011 Albers et al; licensee BioMed Central Ltd.

【 图 表 】

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【 参考文献 】

• [1]Bischoff KM, Skinner-Nemec KA, Leathers TD: Antimicrobial susceptibility of Lactobacillus species isolated from commercial ethanol plants. J Ind Microbiol Biotechnol 2007, 34:739-744.
• [2]Schell DJ, Dowe N, Ibsen KN, Riley CJ, Ruth MF, Lumpkin RE: Contaminant occurrence, identification and control in a pilot-scale corn fiber to ethanol conversion process. Bioresour Technol 2007, 98:2942-2948.
• [3]Skinner KA, Leathers TD: Bacterial contaminants of fuel ethanol production. J Ind Microbiol Biotechnol 2004, 31:401-408.
• [4]Priest FG, Campbell I: Brewing Microbiology. New York, NY: Kluwer Academic/Plenum Press; 2003.
• [5]Gibson BR, Lawrence SJ, Leclaire JP, Powell CD, Smart KA: Yeast responses to stresses associated with industrial brewery handling. FEMS Microbiol Rev 2007, 31:535-569.
• [6]Simpson WJ, Smith AR: Factors affecting antibacterial activity of hop compounds and their derivatives. J Appl Bacteriol 1992, 72:327-334.
• [7]Suzuki K, Iijima K, Sakamoto K, Sami M, Yamashita H: A review of hop resistance in beer spoilage lactic acid bacteria. J Int Brew 2006, 112:173-191.
• [8]Jorgensen H, Vibe-Pedersen J, Larsen J, Felby C: Liquefaction of lignocellulose at high-solids concentrations. Biotechnol Bioeng 2007, 96:862-870.
• [9]Narendranath NV, Hynes SH, Thomas KC, Ingledew WM: Effects of Lactobacilli on yeast-catalyzed ethanol fermentations. Appl Environ Microbiol 1997, 63:4158-4163.
• [10]Stenberg K, Bollok M, Reczey K, Galbe M, Zacchi G: Effect of substrate and cellulase concentration on simultaneous saccharification and fermentation of steam-pretreated softwood for ethanol production. Biotechnol Bioeng 2000, 68:204-210.
• [11]Almeida JRM, Modig T, Petersson A, Hahn-Hagerdahl B, Lidén G, Gorwa-Grauslund MF: Increased tolerance and conversion of inhibitors in lignocellulosic hydrolysates by Saccharomyces cerevisiae. J Chem Technol Biotechnol 2007, 82:340-349.
• [12]Taherzadeh MJ, Gustafsson L, Niklasson C, Liden G: Conversion of furfural in aerobic and anaerobic batch fermentation of glucose by Saccharomyces cerevisiae. J Biosci Bioeng 1999, 87:169-174.
• [13]Raspor P, Goranovic D: Biotechnological applications of acetic acid bacteria. Crit Rev Biotechnol 2008, 28:101-124.
• [14]Albers E, Larsson C: A comparison of stress tolerance in YPD and industrial lignocellulose-based medium among industrial and laboratory yeast strains. J Ind Microbiol Biotechnol 2009, 36:1085-1091.
• [15]Purwadi R, Brandberg T, Taherzadeh M: A possible industrial solution to ferment lignocellulosic hydrolyzate to ethanol: continuous cultivation with flocculating yeast. Int J Mol Sci 2007, 8:920-932.