Proceedings for Microbiology Project

Proceedings

Saccharomyces cerevisiae

S. cerevisiae is an aerobic, single celled organism, commonly known as yeast. This organism is a eukaryotic model organism, and can reproduce sexually and asexually. S. cerevisiae has many uses in industry due to its ability of fermentation. In baking, the production of carbon dioxide is yeast important property, but in bio fuel and alcohol production, the ethanol produced by this organism is the industrial important product.

Three investigations were conducted into this organism. The first experiment conducted was to explore the best substrate for S. cerevisiae to produce alcohol out of glucose, raffinose and maltose. Raffinose was found to be the best to make the cell grow, but glucose was concluded to be the ideal substrate for ethanol production. A side experiment of this investigation was also to see whether more ethanol was produced with glucose depending on if shaking or static conditions were enforced, and it was concluded that static conditions are best for ethanol production yet shaking the culture was better for more growth, as more respiration could take place due to more oxygen available.

The second experiment was also to explore the best substrate for ethanol production, using fructose and lactose in addition to glucose and maltose. Again glucose was found to be the substrate in which most ethanol was produced.

Lastly, the third investigation in to S. cerevisiae was also looking into the best substrate for ethanol production in yeast. Here, glucose, lactose and glycogen were the substrates, and again glucose was found to be the ideal substance. The optimum concentration of glucose was also explored, at 2.5, 5 and 10%, to see which could aid in the highest ethanol production. 10% was found to be the best concentration at producing the most ethanol.

In conclusion, glucose is the best carbon source to use for maximum ethanol production, static conditions are best for ethanol production, and it would be best for a 10% concentration to be used.

I think these finding relate to the alcohol industry, because these result show that glucose is the best carbon source for ethanol production by S. cerevisiae. Although glucose maybe the more expensive option out of the other carbon sources used, it does produce the best ethanol yield.

Gluconoacetobacter zylinium

Gluconoacetobacter zylinium is a gram negative, rod shaped bacteria. This organism produces cellulose as a secondary metabolite. The cellulose produced by this organism is used for the production of dressings and bandages for injuries, as well as for artificial skin for burns and after surgery.

This organism was investigated to try and obtain maximum cellulose production by differentiating growth media. Glucose, fructose and galactose were the three different carbon sources that were used. All three had no ethanol and ethanol added. The cultures were incubated and samples were taken after two and three weeks of growth. The dry weight of cellulose produced was weighed and absorbances were measured for a protein assay.

It was found that there was less growth when ethanol was present than when there was no ethanol, so ethanol may be inhibitory to the growth of the organism. More cellulose was produced with glucose than galactose and fructose.

I think these results are relevant to industry as they show that glucose is the better carbon source to use out of the three used for this experiment. They also show that the addition of ethanol does not benefit the production of cellulose.

Dunaliella salina

Dunaliella salina is a eukaryotic photosynthetic algae. This organism is a halophilic organism, and lives in a marine environment.

D. salina produces two products β carotene and glycerol, in response to stressful conditions for example high salinity, but these two products are not only useful to the organism but also industry. β carotene is a precursor for vitamin A, which is an important vitamin for mammalian growth, and so is industrial important in the pharmaceutical industry. β carotene was reported to be up to ten times more effective as an antioxidant when isolated from D. salina than any other source which demonstrates the importance of this product from this organism. Glycerol is also an important substance in the pharmaceutical industry, and is widely used in numerous products from cough medicines to an aid in clearing oral fungal infections.

An investigation into the maximum production of β carotene was conducted. The optimum temperature and salinity was examined for D. salina to produce the most β carotene. D. salina was grown in artificial seawater with temperatures that ranged from 18 - 42˚C, and a salinity range from 0.6 - 5.6 M. Along side this experiment, the growth of D. salina was also monitored to see if there was a correlation between maximum β carotene production and maximum growth.

In conclusion, increased cell growth was found to not increase β carotene production. It was found that 18˚C was the best temperature and 3.6M was the optimum salinity for β carotene production. The optimum growth was observed at 30˚C and 3.6M.

With relevance to industry, I believe that although increased cell growth did not increase β carotene production in this experiment, to produce large amounts of β carotene a large number of D. salina cells are going to be needed, so although 18˚C was the optimum temperature for β carotene production, and 30˚C was best in terms of growth, an intermediate temperature should be used so both increased growth and production of β carotene are achieved.

Alcaligenes eutrophus

Alcaligenes eutrophus is a bacteria and is a chemolithoautotrophic organism. This organism produces the compound polyhydroxybutyrate (PHB). PHB is usually only produced when there is an abundant source of carbon available, and the organism will utilises this when there is a shortage of other carbon sources. However, this is an important product in the production of plastics.

An investigation into the maximum production of PHB was conducted. The objective was to explore the best carbon source out of glucose of fructose and determine which concentration of these sugars was the optimum concentration for PHB production. 1, 4 and 8% concentrations were used of both sugars. The culture was grown for two days and optical densities were recorded. It was found that fructose was the better carbon source, and 4% was the best concentration of this sugar. At lower