Sciencemadness Discussion Board

Starch fermenting yeast

mnick12 - 29-3-2010 at 17:45

Hello everyone,
So recently I have started working with yeast, and through selective "brewing" as well as induced mutations I am attempting to produce a yeast that is capable of fermenting starches into higher carbon alcohols. I started two days ago with regular bakers yeast, I simply made a sterile molasses water solution and added 5gr of yeast. I put this solution in an incubator at 90 degrees F. It fermented for 1.5 days and some yeast settled at the bottom of the container, then I took a 250ml e flask and added 100mg of ammonium nitrate 500mg of ammonium phosphate and 200mg of ammonium sulfate. These are the nutrients I chose to use because it is all I had on hand, and for the sugar I used 30gr of glucose syrup and 200ml of water. I took the yeast solution and poured it into the new solution without letting the yeast that settled in the container go into the new solution. The new solution has been fermenting for a little over half a day, and I am now going to add a few grams of starch along with a small amount of nitroso-urea solution. The reason why I am doing this is because I have a feeling there may be some yeast in there that can ferment starch but not very well, and by causing mutations with nitroso-urea I may get some beneficial mutations.
I will continue to monitor the yeast and as the days go on I will continue to mutate a remake yeast solutions until I get one that can ferment starch.
Any comments are welcome, and I could post pics if you want but they would be kinda boring.

not_important - 29-3-2010 at 19:36

You need to be very careful not to pick up contamination from wild fungi and bacteria that would normally be out competed by the yeast; but which would find a foothold as the sugar is exhausted. That might result in a mixed culture where its the intruding organisms doing the starch hydrolysis.

from 1978:
Quote:
Genetic studies were made on the genes determining the ability to ferment starch (STA) in five strains of S. diastaticus different in origins, strain IFO 1046, IFO 1015, Y 8, Y 13 and C1372. With the heterothallic strain IFO 1046, the genes STA1 and STA2 were separated by single spore cultures and crosses to S. cerevisiae. Strain Y 8 did not sporulate, but the progeny having gene STA3 was isolated from the hybrid between the respiratory deficient mutant of strain Y 8 and S. cerevisiae obtained by the minimal plate mating technique. Strain IFO 1015 was the homothallic strain. The progeny having gene STA4 was isolated from the hybrid between IFO 1015 and S. cerevisiae. Strain Y 13 did not sporulate, but the progeny having gene STA5 was isolated according to the same technique as applied to strain Y 8. Haploid strain C1372 retained the gene STA6. The genes STA1 and STA4, and STA3, STA5 and STA6 were shown to be not separable by tetrad analysis.
These results demonstrate the existence in S. diastaticus of at least 3 polymorphic genes for starch fermentation; STA1 (STA4), STA3 (STA5 and STA6), and STA2, and these STA genes are located on different linkage groups.


Genetic studies of ability to ferment starch in Saccharomyces: Gene polymorphism
http://www.springerlink.com/content/u55387211j6g58m4/



2006

A rapid method for recognising strains of yeast able to hydrolyse starch or dextrin

http://www3.interscience.wiley.com/journal/119577946/abstrac...


and 2000, roll your own:
Quote:
Alcohol fermentation of starch was investigated using a direct starch fermenting yeast, Saccharomyces cerevisiae SR93, constructed by integrating a glucoamylase-producing gene (STA1) into the chromosome of Saccharomyces cerevisiae SH1089.


Alcohol fermentation of starch by a genetic recombinant yeast having glucoamylase activity

http://www3.interscience.wiley.com/journal/71003769/abstract

ElectroWin - 4-10-2012 at 09:46

i hear that the kind of alcohols made by the organism depends a lot on what you feed it. Pectins, for instance, produce methanol.

I started a wild yeast last week, one collected from the bottom of a bag of black beans that had been sitting around for over a year. I am starting with a simple experiment: to see if this organism can survive on sucrose alone, and for how long.

I put a pinch of the yeast pellets into a 500 mL bottle of cold, Toronto tap water that had about 50 mL white sugar dissolved in it (apparent specific gravity 1.046), sealed it, and set it on my kitchen counter in an out-of-the-way place.

After a few hours it appeared to be quite active, as it warmed up, with about 100 small pellets migrating between the bottom and the surface; at 48 hours all the yeast appeared to have died, and settled to the bottom, but i left it.
Now at 8 days, there is some activity again.

The plan, now, is to take the survivors and inoculate more bottles, each with a different kind of solution.

Some time later, they will be re-introduced to each other. It should be possible, through selective breeding, to reach an organism that will be hearty and produce plenty of alcohol from anything i throw at it.

unionised - 4-10-2012 at 10:02

"I started a wild yeast last week, one collected from the bottom of a bag of black beans that had been sitting around for over a year."
How do you know it's a yeast?

ElectroWin - 4-10-2012 at 10:39

Quote: Originally posted by unionised  
"I started a wild yeast last week, one collected from the bottom of a bag of black beans that had been sitting around for over a year."
How do you know it's a yeast?


qualitatively. its appearance precisely matches what you find in commercially available packets of yeast.. as well as its behaviour during fermenting.