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  • Difficulty achieving high cell concentrations during propagation.

    I'm hoping to get a response from a Lallemand representative on this one.

    Our Brewery has decided to explore the possibility of propagating up pitchable quantities regularly to reduce our need to harvest from tank bottoms.
    To make the whole process work we need to achieve about 200 Million cells/ mL in the final propagator slurry.
    We have conducted several test propagations varying between 3 and 10bbl- some of which have been agitated and some have not.
    We started in the small 3bbl tanks and have moved to the 10bbl agitated vessel and slowly changed conditions with each test.
    Specs are as follows-
    10 degree plato all malt wort
    pitched at 8.5 Million cells/mL
    Temperature held at 75F
    Continuous flow of sterile O2
    Continuously agitated (10bbl only)
    Standard fermentation quantity of yeast nutrient added to kettle

    Early on we realized we weren't adding nearly enough Oxygen which was an easy fix

    Each prop. hits terminal gravity in about 24 hours but fails to breach 100Million cells/ml.

    We have actually pitched a couple large tanks with said propagator slurry with equal or greater fermentation characteristics (which is partially successful).

    I don't know what is holding us up from the 200Mcell/ml mark and the agitation didn't seem to make much of a difference in growth.

    I feel like I am using adequate Oxygen so I will mark that off.
    With that being said I feel like there must be other nutrients holding up cell growth. Amino acids and other nutrients (Zn, Nitrogen, etc.).
    With that idea I considered increasing the wort gravity but if this works that won't really be an option when put in to full production mode.
    So the next thought is to load on the yeast nutrient. If my thinking is correct here what nutrient blend would you recommend and how much over standard fermentation addition rates would you recommend?

    Is there something I'm overlooking?

    Thanks and let me know if I left out any important details.

    N

  • #2
    I don't have any direct experience with this, but it sounds like you need to use far lower-gravity wort to get the yeast to respire instead of ferment (whether you have the tank volume to do that is another question). If you have access to the MBAA Technical Quarterly archives, you should look for a 2003 article called "Yeast Management Under High-Gravity Brewing Conditions" by Mike Cholerton (it's in vol. 40 no. 3). If his method is still the norm, you probably won't want to go much above 100 mcells/mL anyway so your yeast vitality is as high as possible.

    Joe

    Comment


    • #3
      10 plato should be about perfect. Temp could be higher if you have a good chilling system.

      My first thought would be nutrients. Zinc and calcium will be the big ones. If I remember right our calcium levels are about 40ppm on prop wort. I like my zinc to be higher than 0.1-.15 range for normal beers and we double that for our prop. From my studies with zinc about half will drop out with the trub when added 15 min till the end of the boil. Our nutrient levels are pretty low so we have a nutrient blend that we add from wyeast. Double the suggested rate for your prop and you should be good.

      My second thought would be O2 issues. Are you pulling straight O2 or is it filtered air? If you are using pure O2 you might be killing of some yeast if your ppm gets to high. We just use filtered air here and it works great. Our air line is also attached to a DO probe that turns it off and on. Do you have a similar set up? If your O2 level gets to low the yeast will go fermentative and it is hard to switch back.

      You might try to do 2.5bbl of prop wort on the first day to get your yeast into exponential growth phase and then top it up with 7.5bbls of wort the next day.

      Comment


      • #4
        It looks like you want to go from a 10 bbl propagation to a 150 bbl ale pitch or a 100 bbl lager pitch. I believe with your setup, 200M cells/ml or more (strain dependent) is achievable and perhaps the hold back is pitching rate. I have found that 40 to 60M cells/ml will achieve the optimum yield for propagation and this is backed up by Chris White in his book "Yeast".

        As gbrower suggested, pure continuous 02 could create problems. I too use sterile air but in a continuous flow. I have read that you can't get too much O2 from air but regulating it with a DO meter would be ideal and perhaps reduce foaming. I adjust the flow by the foam rate (cowboy, I know). I also use Wyeast nutrient at 2X fermentation rate.

        Caveat- I am not a professional brewer but an extreme yeast enthusiast who would like to someday work in brewing yeast management. I signed up for this board specifically to try to help with this issue and had to plead to be accepted because I believe these suggestions will help. I do have a 15 gallon propagation vessel and have propagated 10 bbl pitches for a local brewery. My system will achieve 250 - 340M cells/ml (strain dependent).

        So here is my suggestions for 200M+ cells/ml:

        1) 10 degree Plato wort
        2) ~40M cells/ml pitch
        3) Continuous AIR
        4) Continuous agitation
        5) 2X Wyeast Nutrient or comparable
        6) 75 - 80F Propagation Temp

        I truly hope this helps. Please post back if you try it.

        Mark

        Comment


        • #5
          I have talked to a few of our scientists at Lallemand regarding this question, and the main parameters that struck them as possible issues were:
          1. the use of pure oxygen, too much pure oxygen can actually be detrimental to the yeast, it is better to use a filtered air supply for propagation if possible.
          2. your method of oxygenation/aeration, are you getting sufficient levels of oxygen being dissolved? Or is it just bubbling through and not getting to the yeast?
          3. As for the nutrients, I would recommend something with Zinc (Servomyces) and FAN and Mg (Fermaid).
          Please feel free to send an email if you have any additional questions.
          cparnin@lallemand.com
          Cheers!
          Caroline

          Originally posted by Noble View Post
          I'm hoping to get a response from a Lallemand representative on this one.

          Our Brewery has decided to explore the possibility of propagating up pitchable quantities regularly to reduce our need to harvest from tank bottoms.
          To make the whole process work we need to achieve about 200 Million cells/ mL in the final propagator slurry.
          We have conducted several test propagations varying between 3 and 10bbl- some of which have been agitated and some have not.
          We started in the small 3bbl tanks and have moved to the 10bbl agitated vessel and slowly changed conditions with each test.
          Specs are as follows-
          10 degree plato all malt wort
          pitched at 8.5 Million cells/mL
          Temperature held at 75F
          Continuous flow of sterile O2
          Continuously agitated (10bbl only)
          Standard fermentation quantity of yeast nutrient added to kettle

          Early on we realized we weren't adding nearly enough Oxygen which was an easy fix

          Each prop. hits terminal gravity in about 24 hours but fails to breach 100Million cells/ml.

          We have actually pitched a couple large tanks with said propagator slurry with equal or greater fermentation characteristics (which is partially successful).

          I don't know what is holding us up from the 200Mcell/ml mark and the agitation didn't seem to make much of a difference in growth.

          I feel like I am using adequate Oxygen so I will mark that off.
          With that being said I feel like there must be other nutrients holding up cell growth. Amino acids and other nutrients (Zn, Nitrogen, etc.).
          With that idea I considered increasing the wort gravity but if this works that won't really be an option when put in to full production mode.
          So the next thought is to load on the yeast nutrient. If my thinking is correct here what nutrient blend would you recommend and how much over standard fermentation addition rates would you recommend?

          Is there something I'm overlooking?

          Thanks and let me know if I left out any important details.

          N

          Comment


          • #6
            some yeast will not have as high of a growth potential as others as well.

            10-12ยบ wort is fine but I'm willing to bet pure O2 is your problem. also you should make sure your air isn't just going straight up but rather is diffusing well.
            I hope I encouraged you!

            Comment

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