Maybe someone can propose the growth conditions for saccharomyces cerevisiae in laboratory fermenter? I need to obtain the high biomass of this yeast. At this moment I prepared a medium containing 20g/L glucose, 10 g/L peptone and 5g/L yeats extract. Is there enough of these substances for S. cerevisiae growth? And what about other parameters - pO2, air, pH?
Hi Dovile,
some period ago we tried biomass obtainment process for S. cerevisiae DY7221 commercial strain devised for ethanol production. We used fed-batch process. Batch and fed-batch medias consisted from sugar beet molasses, macro- /micro- salts and D-destiobiotin. Within process (~28 h) we got biomass increase till ~60 g/l. Initial biomass concentration at the beginning of process was 5 g/l. We used the same equipment you have.
Information about process conditions, including media composition and applied feeding profile, you can find in attached article (Eng. Life Sci. 2013, 13, No. 2, 172–184).
Cheers, Oskars
Article Model-based optimization and pO2 control of fed-batch Escher...
I agree with previous answers, the key is to set the proper glucose feed, as stated by Mathias, at first log feed according to growth and shifting to flat rate for about the last 24 hours. With a slight head pressure of 0,5 bar to increase oxygen solubility we have reached in excess of 100 g/L of biomass in 48 hours. But be careful, head over pressure is not safe in glass reactors. To avoid crabtree effect you need to avoid increasing glucose concentration higher tan 1 g/L (values near not detectable should be preferred) and also keep dissolved oxygen over 15% (you will need something like 12 hours of growth to get down to this value). You can start aeration at 0.5 vvm and after 12 hours increase to 1 or 1.2 vvm. Optimum pH to grow yeast is 4.5 to 5.0. Yields of 0.45 g of yeast /g of glucose are usual in practice. But if your focus is just biomass for lab purposes, maybe the glucose yield is not so critical and you can allow some losses in fermentation to ethanol. I do not reccomend you to use industrial raw materials as molasses for lab applications because they need to be treated to remove toxic compounds, and are difficult to get at small quantities. Best use crystalline dextrose for food applications that you can get in 25 Kg sacks at about 10-20 euro/Kg deppending of supplier. You can prepare a 60% w/w solution in water and get it sterilized separately in the autoclave. For producing 100 g/L of yeast in 10 L of culture you may need near 5 Kg of feed solution. As stated by Oskars, you may need to put a mineral salt solution plus magnesium and phosphate salts to your base medium to allow growth at high cell densities. Consider the average elemental composition of the yeast to balance the medium or get a base fed batch medium recipe. We did not put biotin but used corn steep solids (trade name Solulys from Roquette) as a complex nitrogen source providing also vitamins for growth.
Good luck!!
I believe that you have a lot of good advises to growth your yeast in lab, but to optimize for your yeast, you have to try and change some of the variables. Ex. For the yeasts we isolated and selected for ethanol production in industrial scale, they do not need biotin. Each strain could be a litle different in their necesity to growth, and the way you do it. My advise is to do what most of the people advised you to do in the previous comments, and try to improve yoursef for your yeast.
Thank you all for the information....How to obtain high biomass yield of baker's yeast on hyperosmotic media (yeast extract 5 g/L, peptone 5 g/L and sucrose: 200 g/L)?
Well, at the onset baker's yeast fermentation is a fed batch process. Here the critical substrate is not the carbohydrate (like glucose or sucrose)but oxygen. Note when the DO falls below a particular level the yeast will switch over to fermentative mode of energy generation and then the biomass will not be baker's yeast. You should monitor the DO in the fermenter and not the carbohydrate concentration.
@Jai Ghosh Sir, I am working on an experiment where I can improve the leavening ability of baker's yeast using hyperosmotic media, but the problem is with hyperosmotic media the yield is less...How can yield improvement and hyperosmotic treatment can be done at the same time?
As I said before and I repeat it here again that you must first standardize the process of regulating the DO level in the fermentation. Once you have optimized that, (i.e. not to allow the DO to fall below the critical level which would not generate bakers yeast, though you may get a good biomass) then proceed with adaptation to 200,000 ppm of sucrose tolerance.
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