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The potiential of the probiotic Saccharomyces boulardii to produce bioethanol in lignocellulosic conditions

Ljung, Elin LU (2016) KMB820 20161
Applied Microbiology
Biotechnology
Abstract
Today, bioethanol is predominately produced with conventional feedstock that may not be desired for ethanol production due to their primary food and animal feed value. Therefore, lignocellulosic biomass, a relatively cheap and non-food competitive biomass has received attention. However, the complexity of lignocellulosic biomass poses challenges to developing a large-scale production process competitive with conventional bioethanol production. One of the major problems is the lignocellulosic inhibitors, formed during biomass pre-treatment under harsh conditions, which affects the fermentation capacity of yeast and consequently the efficiency of production. To improve production efficiency, simultaneous enzymatic degradation of... (More)
Today, bioethanol is predominately produced with conventional feedstock that may not be desired for ethanol production due to their primary food and animal feed value. Therefore, lignocellulosic biomass, a relatively cheap and non-food competitive biomass has received attention. However, the complexity of lignocellulosic biomass poses challenges to developing a large-scale production process competitive with conventional bioethanol production. One of the major problems is the lignocellulosic inhibitors, formed during biomass pre-treatment under harsh conditions, which affects the fermentation capacity of yeast and consequently the efficiency of production. To improve production efficiency, simultaneous enzymatic degradation of lignocellulosic biomass and fermentation of sugars can be performed. But this poses some limitations, due to higher optimal temperatures of the enzymes than for yeast. Low pH is another parameter that could reduce ethanol production in the presence of inhibitors, however, it can also reduce the risk of bacterial contamination. In this study, the probiotic yeast Saccharomyces boulardii was evaluated for production of lignocellulosic bioethanol, since in previous studies it has been stated that it tolerates low pH and elevated temperatures. For this purpose, the S. boulardii strain ATCC MYA-796 was exposed to different pH and temperature conditions, and lignocellulosic inhibitors. The S. cerevisiae strains CEN.PK 113-7D and TMB3500 were used for comparison. The pH and temperature tolerance of S. boulardii did not contribute to a significantly differentiated behaviour than that detected for CEN.PK 113-7D. Also, the strains showed equally good ability to cope with lignocellulosic inhibitors. What distinguished the behaviour of ATCC MYA-796, and to some extent CEN.PK 113-7D, from that of TMB3500 was the lack of post-diauxic growth at cells cultivated at temperatures above 30 ºC. An investigation of what is causing this phenomenon could provide novel insights about this strain and the diauxic shift. (Less)
Popular Abstract
To develop fuels that can support the worlds growing energy demand and at the same time have low negative environmental impact is crucial for the future wellbeing of the world. A promising fuel is bioethanol that is produced from agricultural waste or forest residues by living organisms.

Yeast is a small organism that probably most people have used, maybe to get the perfect texture of a cake or to make an alcoholic beer. It is the capability of the yeast to ferment, or in other words, convert sugars into ethanol or alcohol as we normally call it, that makes the yeast useful in a variety of applications. We have evaluated a yeast’s potential to convert sugars in plants into ethanol, which further can be used as a fuel.

During the last... (More)
To develop fuels that can support the worlds growing energy demand and at the same time have low negative environmental impact is crucial for the future wellbeing of the world. A promising fuel is bioethanol that is produced from agricultural waste or forest residues by living organisms.

Yeast is a small organism that probably most people have used, maybe to get the perfect texture of a cake or to make an alcoholic beer. It is the capability of the yeast to ferment, or in other words, convert sugars into ethanol or alcohol as we normally call it, that makes the yeast useful in a variety of applications. We have evaluated a yeast’s potential to convert sugars in plants into ethanol, which further can be used as a fuel.

During the last decades, the global energy demand has increased as well as the awareness that fossil fuels greatly contributes to a global climate change. Alternative fuels that both support this growing energy demand and have a lower environmental impact, have therefore received interest. An example is bioethanol, which is ethanol that is a product of the biological fermentation process that occurs with yeast. It is derived from sugars in plants or plant-derived material, which is called biomass. Today, bioethanol is predominately produced from sugar cane and corn. However, this may not be desirable for ethanol production due to its primary use as food and animal feed. Therefore, lignocellulosic biomass, which is a non-food competitive biomass constituted of agricultural waste and forest residues, has received attention. However, the complexity of lignocellulosic biomass requires new solutions to develop a process which is competitive with bioethanol production from sugar cane and corn. A problem is the lignocellulosic inhibitors, which are formed during the break-down of the sugars in the biomass. They reduce the fermentation capacity of yeast and consequently the efficiency of production. A solution to increase the production efficiency is the use of enzymes to release sugars from the biomass and at the same time let the yeast ferment. But this poses some limitations, due to higher optimal temperatures for enzyme activity than of yeast. To overcome this problem, heat tolerant yeast could be used. High acidity during the fermentation could also contribute to a more efficient process, as it reduces the risk of contamination.

We studied a probiotic yeast, which when eaten can provide health benefits such as reducing diarrhea. This probiotic yeast has been proven to be able to withstand high acidity and temperatures – just as in our stomachs. We wanted to investigate if these abilities of the yeast could be advantageous for bioethanol production from lignocellulosic biomass. For this purpose, the probiotic yeast was exposed to different levels of acidity and temperatures, as well as lignocellulosic inhibitors. A yeast that is frequently used in bioethanol production was used for comparison. The results did not display any differences between the two yeast species when they were exposed to an acidic and hot environment. Neither did the probiotic yeast strain show higher ability to cope with lignocellulosic inhibitors. In conclusion, this probiotic yeast does not distinguish itself as more promising for bioethanol production under the examined circumstances. (Less)
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author
Ljung, Elin LU
supervisor
organization
course
KMB820 20161
year
type
H2 - Master's Degree (Two Years)
subject
keywords
lignocellulosic inhibitors, bioethanol, Saccharomyces boulardii, Saccharomyces cerevisiae, elevated temperature, low pH, diauxic shift, applied microbiology, teknisk mikrobiologi
language
English
id
8885272
date added to LUP
2016-06-29 13:34:40
date last changed
2016-06-29 13:34:40
@misc{8885272,
  abstract     = {Today, bioethanol is predominately produced with conventional feedstock that may not be desired for ethanol production due to their primary food and animal feed value. Therefore, lignocellulosic biomass, a relatively cheap and non-food competitive biomass has received attention. However, the complexity of lignocellulosic biomass poses challenges to developing a large-scale production process competitive with conventional bioethanol production. One of the major problems is the lignocellulosic inhibitors, formed during biomass pre-treatment under harsh conditions, which affects the fermentation capacity of yeast and consequently the efficiency of production. To improve production efficiency, simultaneous enzymatic degradation of lignocellulosic biomass and fermentation of sugars can be performed. But this poses some limitations, due to higher optimal temperatures of the enzymes than for yeast. Low pH is another parameter that could reduce ethanol production in the presence of inhibitors, however, it can also reduce the risk of bacterial contamination. In this study, the probiotic yeast Saccharomyces boulardii was evaluated for production of lignocellulosic bioethanol, since in previous studies it has been stated that it tolerates low pH and elevated temperatures. For this purpose, the S. boulardii strain ATCC MYA-796 was exposed to different pH and temperature conditions, and lignocellulosic inhibitors. The S. cerevisiae strains CEN.PK 113-7D and TMB3500 were used for comparison. The pH and temperature tolerance of S. boulardii did not contribute to a significantly differentiated behaviour than that detected for CEN.PK 113-7D. Also, the strains showed equally good ability to cope with lignocellulosic inhibitors. What distinguished the behaviour of ATCC MYA-796, and to some extent CEN.PK 113-7D, from that of TMB3500 was the lack of post-diauxic growth at cells cultivated at temperatures above 30 ºC. An investigation of what is causing this phenomenon could provide novel insights about this strain and the diauxic shift.},
  author       = {Ljung, Elin},
  keyword      = {lignocellulosic inhibitors,bioethanol,Saccharomyces boulardii,Saccharomyces cerevisiae,elevated temperature,low pH,diauxic shift,applied microbiology,teknisk mikrobiologi},
  language     = {eng},
  note         = {Student Paper},
  title        = {The potiential of the probiotic Saccharomyces boulardii to produce bioethanol in lignocellulosic conditions},
  year         = {2016},
}