Continuing the yeast experiments

Now that the winter solstice festivities are over, I can get back to doing some science.

The large variability in the yeast experiments, in both experimental and control groups, is disappointing.
However, my data still fits with Motta's results. Indeed, in his experiments, the 110mT group only had a small CO2 overpressure with respect to control. There was a 30% overpressure only in the 220mT group and only after many hours. Also, a biologist friend of mine pointed out that, in the Motta experiments, the pH was regularly adjusted by hand in both groups. Indeed, increase of CO2 partial pressure would lead to acidification of the growth medium. However I cannot do that since I cannot open the flasks without losing the pressure value.

Another point of concern that has been pointed to me is that the yeast are very sensitive to temperature, and I did not take any measures against air currents.

To avoid all these problems, I will take the following measures in the next experiment.

• The flasks will be enclosed in a plastic box to eliminate current drafts.
• The plastic box will be covered in aluminum foil to protect the flasks from light.
• Each flask will be connected to an empty 330mL Perrier bottle. This will increase the volume to about 400mL, which should:
• Absorb small variations due to the
• Decrease total pressure, leading to less effect on medium pH, and reducing the incidence of leaks
  
• The flasks will be washed with chlorine bleach before the experiment.
• I will use boiled water.
  
• I will use 0.9% glucose.
• I will use two square magnets to double the field.

Litterature on the effect of static magnetic fields on yeast growth

The effect of magnetic fields on the growth of Baker's yeast has, of course, already been studied, but a surprisingly low number of times. I found only a handful of references.

I found some mentions of Pasteur conducting experiments on the effect of magnet on the fermentation of wine. His collected works are available at Bibliothèque Nationale de France but only in non-OCR form. They are quite lengthy and lack an index. I didn't have the patience to read all the 600 pages.

Amongst the more recent studies are a positive report by Brazilian researchers. As you may know, Brazil has some interest in ethanol production by fermentation. The article is well-referenced and is even available here.

Biotechnol Prog. 2001 Sep-Oct;17(5):970-3.
Changes in Saccharomyces cerevisiae development induced by magnetic fields.
Motta MA, Montenegro EJ, Stamford TL, Silva AR, Silva FR.

Departamento de Biofísica e Radiobiologia, Universidade Federal de Pernambuco, Cidade Universitaria 50670.901, Brazil.

Saccharomyces cerevisiae cultures exposed to 110 mT and 220 mT steady magnetic fields (SMF) were studied to observe eventual induced growth alterations and changes in metabolic activity. Cell mass (biomass) growth was evaluated by light spectrometry, and metabolic alterations were estimated on the basis of the CO2 pressure produced and by the culture media pH changes, measured at the beginning and the end of the observation. The yeast strain DAUFPE-1012, cultivated in a nonaerated liquid agar Sabouraud glucose medium, was exposed to SMF generated by NdFeBr magnets. Results showed alterations induced by 220 mT SMF as an increment in cell proliferation (1.84%) and an increased CO2 production (36.1%) as compared to control groups. Furthermore, the initial-to-final pH difference in 220 mT SMF exposed cultures was higher than the 110 mT SMF and the control values. The whole acidification and the rise in CO2 production observed after 220 mT SMF exposure did not correspond to the biomass growth values, as compared to the other cultures, and was apparently provoked by a enhancement in the cellular metabolic rate. This technique becomes very promising for future biotechnological applications in fermentative processes.

PMID: 11587592 [PubMed - indexed for MEDLINE]

The following patent is also interesting:
Apparatus and method for exposing seeds to a magnetic field.

Replication of yeast experiment

I have trimmed the tubes to equalize their inner volume to about 12 ml. I am now repeating yesterday's experiment, but using south poles. I took all mesures to avoid the previously mentioned pitfalls.

Here are the results.

South-pole treated samples slightly outperform untreated samples; the difference is not very significant. But there is more.

First, although I trimmed the larger, green silicone tubes so that they have the same volume as the others, they still consistently give higher results -- see the upper two curves.

Second, there is significantly more variability in the control group than in the treatment group. I think this might be due to light. I simply put a drape over the flasks in an attempt to uniformize the amount of light they receive. However, the higher control flask that is not using a large tube sits in the shadow of a distant compact fluorescent lamp, while the other flasks do not.

Tomorrow, I will build an opaque box to protect the flasks.