Re: [DIYbio] Isothermal microcalorimetry for bacterial activity.

Hi John,

>What strikes me is your aim is to measure very dilute solutions and I
wonder what "containing bacteria" means?

A sample of sludge (flocs of sludge).

The type of sludge formed in activated sludge system for wastewater
treatment (http://www.iwa100as.org/history.php).

This sludge is composed of bacteria, protozoa and other microorganisms
(http://www.engitech.com/asm.htm).

>Are the bacteria fixed, or do they wash away? If they are fixed on a
surface, there's a chance.

In principle I was not planning on using sessile bacteria in biofilms.
But only flocs of sludge in suspension.

> How do you reconcile adiabatic and aerated? How do you reconcile
adiabatic and "fed by"?

The aeration would be maintained only in bioreactor to keep a stock of
biomass for analysis.

The analysis would be done only with a sample of sludge injected in an
adiabatic compartment that would be maintained without aeration during
the measurements and diluted with the areated efluent to be analysed.

The same amount of sludge would be injected in other adiabatic
compartmente diluted with aerated water.

The dissolve oxygen in efluent and water (both previously aerated) would
keep the metabolism during the analysis time. (I expect :^)

I supose that in the reference compartment (with water and no
nutrients*) would happen only endogenous respiration.

*As nutrients I mean the organic load in the effluent that would be
analyzed.

I do not plan to measure absolute values of heat, but only "temperature
differences" between the two compartments (with nutrients and no nutrients).

You think it might be more appropriate to use biomass fixed on a solid
support?

But in this case how I could provide the same amount of biomass in the
two compartments (with nutrients and without nutrients)?

To control the analysis the difference in heat released in compartments
should be the result only of the difference in the concentration of
nutrients (organic load in the effluent) and not by the difference in
biomass.

Thanks for your comments.

Best Regards,
Markos


On 15-04-2015 17:15, John Griessen wrote:
> On 04/14/2015 03:03 PM, Simon Quellen Field wrote:
>> Would be possible to use a NTC thermistor, and Arduino for data
>> acquisition, for detecting temperature changes in a medium
>> containing bacteria and nutrients in a DIY approach?
>>
>> Has anyone had any practical experience with this technique?
>
> I've used thermistors. Not like you want to.
>
> They vary from part to part a lot. The sensitivity might be OK. What
> strikes me
> is your aim is to measure very dilute solutions and I wonder what
> "containing bacteria" means?
>
>
> " heat dissipated by bacterial metabolic processes in an adiabatic
> environment measured with thermistors to estimate the organic load in
> wastewater. Imagine keeping an aerated bioreactor containing
> bacteria fed by domestic effluents."
>
> Are the bacteria fixed, or do they wash away? If they are fixed on a
> surface, there's a chance.
>
> Insulation against heat flow is a very big thing in this setting
> because the thermal mass of the
> whole experiment is huge compared to the bacteria mass in aggregate.
>
> How do you reconcile adiabatic and aerated? How do you reconcile
> adiabatic and "fed by"?
> Is the aeration all just recycled gas inside the reactor with no ins
> or outs of gases?
> Do you seal up the system and watch its temperature and pressure
> change for a while -- that's
> what we usually call adiabatic...
>
> Here's an idea: Reduce the heat sink mass surrounding the supposedly
> fixed bacteria. Aeration can stir a vat of
> solution, but for exposing it to the bacteria flow a small trickle of
> it over them in a thin sheet so
> it does not carry away much heat. Measure differential temperature of
> the in and out drip of solution
> flowing over the bacteria surface.
>
> If the bacteria are not fixed, just washing around in solution, then
> the above is no help, and bioreactor
> insulation is almost everything.
>
> (You still need the nice stable temp sensor system to measure heat
> generation...)
>

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