Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!wuarchive!zaphod.mps.ohio-state.edu!ub!kitty!larry
From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: sci.bio
Subject: Re: rule of thumb
Summary: Not a simple matter...
Message-ID: <3983@kitty.UUCP>
Date: 30 Aug 90 02:22:17 GMT
References: <12614@encore.Encore.COM>
Organization: Recognition Research Corp., Clarence, NY
Lines: 45

In article <12614@encore.Encore.COM>, soper@maxzilla.encore.com (Pete Soper) writes:
>   Is there a rule of thumb for estimating the effect of temperature
> on the metabolic rate of simple organisms like yeast?  That is, if
> I have the temperature and rate of CO2 production during the course
> of a fermentation, can I apply a correction to roughly predict what 
> the flow would have been at (say) 3 degrees C higher or lower
> temperature?

	I don't believe there is any simple "rule of thumb" to give you
any quantitative data in answer to your question, based upon the data
you have available.

	To simplify this discussion, I will assume that "rate of growth"
for a given microorganism is directly proportional to the amount of CO2
evolved for a given biomass.  Let's also assume that we are dealing
with mesophiles, although what I am stating is not much different for
lower or higher temperature organisms.

	For any given microorganism there is a temperature at which
maximum rate of growth occurs.  Consider that a common yeast organism,
such as Saccharomyces cerevisiae with a growth medium of molasses
may have a temperature of say, 30 deg C at which maximum growth rate
occurs.  The rate of growth gets really non-predictable within only a
few degrees C *above* this temperature.  The rate of growth *below*
this temperature is roughly logarithmic until we approach a minimum
temperature at which growth can no longer occur.  Depending upon the
particular microorganism, this logarithmic region may extend below
the temperature for maximum growth for perhaps 10 to 20 deg C, below
which we again get unpredictable.

	While I have stated that over a limited region the rate of growth
(and hence CO2 evolution) is roughly logarithmic, I would not at all be
comfortable making any predictions merely based upon knowing CO2 flow
rate at a given temperature.  There are other factors to be considered,
including but not limited to: (1) specific growth rate (u); (2) culture
density; and (3) yield (i.e., grams per gram of substrate).

	For a given biomass and for a given reactor, growth versus
temperature curves would be rather empirical.  I have seen such data
in my travels, and some curves look really *ugly* - i.e., nothing
which anyone could readily predict without actual measurement.

Larry Lippman @ Recognition Research Corp.  "Have you hugged your cat today?"
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