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Unformatted text preview: Analysis of Fungi Growth on Non-Preservative Containing Bread Jenine Hajjar BI 101 H, Honors General Biology October 12, 2007 Abstract
The purpose of this experiment was to investigate different variables which would either negatively or positively affect the growth of mold on bread samples. This experiment considered six different variables: the effect of refrigeration, salt, vinegar, water, sugar, and darkness on the growth of mold on bread. There was also the control which was simply placed alone in a bag. The type of bread used worked very well with this experiment because this bread did not have any preservatives in it. Therefore, this made the mold grow fast without having to surpass preservation chemicals. This experiment involved placing seven 6.4 cm in diameter round pieces of bread in individual vacuum sealed bags. The bags had either salt, vinegar, water, sugar, or nothing placed in them. Three times a week for three weeks, we measured the area of mold on the surface of each different variable and the control. The more time that went by the more mold was present on each piece of bread. Salt, vinegar, sugar, and refrigeration served as a type of preservation; therefore, there was no mold growth on those four variables. The control experienced rapid mold growth while the water and refrigeration both increased steadily. The only reason the levels of mold began to level off near the end of the experiment was that there simply was no more bread for the mold to cover. Introduction
Fungi are rapid growing organisms which rapidly reproduce by releasing spores. Fungi are generally thought of as unwanted invaders that destroy food, clothes, and even our skin. There are many treatments for different fungal infections and it always seems that fungi are simply something that needs to be destroyed (Jung HJ 2007). However, there is much more to fungi than simple destruction. Without fungi, much of the world would be covered in waste because it is a major decomposer in our ecosystems. Not only do fungi decompose waste, they also serve as a source of food for small animals. Instead of ingesting their food, they absorb it through their cell walls and membranes (Borst, 2007). Fungi, like animals, are heterotrophs, therefore they cannot make their own food. Since fungi do not ingest their food, they instead digest it while it is still in the environment. In order to do this, fungi release exoenzymes, which break down complex molecules in order to absorb nutrients (Campbell CD-ROM, 2006). Materials and Methods
Each student was given two or three pieces of bread to cut out seven 6.4 cm circles, using circular cookie cutters. The experiment was observing the growth of mold on differently stored pieces of bread. At the start of the experiment, one piece of bread was placed alone in a bag, removing as much air as possible, this was the control. Then four millimeters of water was added to one bag with a piece of bread and four millimeters of vinegar was added to another bag with a piece of bread. Three and half grams of sugar were added to a fourth bag and three and a half grams of salt were added to a fifth bag. A sixth and seventh bag were placed alone in bags and as much air as possible was removed. The sixth bag was placed in a black light proof plastic bag and the seventh bag was placed in a refrigerator. The sixth other bags were stapled to a poster board and observed for three weeks (Borst, 2007). The amount of mold which had grown was then measured three times a week for approximately three weeks. The only mold measured was the surface mold on the front of the samples. Results
Table 1.1 Quantitative Results of Mold Growth on September 28, 2007.
5 Sep 0.0 0.0 0.0 1.0 0.1 0.0 0.1 7 Sep 0.0 0.0 0.0 9.0 2.0 0.0 1.0 10 Sep 0.0 0.0 0.0 31.0 10.0 0.0 3.0 12 Sep 0.0 0.0 0.0 50.0 18.0 0.0 10.0 14 Sep 0.0 0.0 0.0 61.5 21.0 0.0 13.0 17 Sep 0.0 0.0 0.0 66.0 29.0 0.0 30.0 19 Sep 0.0 0.0 0.0 69.0 33.0 0.0 36.0 24 Sep 0.0 0.0 0.0 73.0 39.0 0.0 71.0 26 Sep 0.0 0.0 0.0 74.0 41.0 0.0 75.0 28 Sep 0.0 0.0 0.0 75.0 42.0 0.0 76.0 Refrigerat or Salt Vinegar Control Water Sugar Dark Figure 1.1 Mold growth on bread containing no preservatives Table 1.1 was the measurements of the amount of mold that had grown on over a period of about three weeks. Figure 1.1 gives a more visible view of the collected data. The samples of bread that contained some sort of preservative did not have any mold grow on them. Initially the sample in darkness grew mold rather slowly, until about 10 days after the experiment had begun. Then the growth rate increased rapidly. The sample containing water had a continuous rate of growth while the control's growth rate skyrocketed initially and then leveled off when the piece of bread was completely covered in mold. Discussion Mold is a fast growing fungus that grows as mycelia and reproduces asexually by producing spores (Campbell, 2005). The spores that are released are the reproductive, survival and infection bodies of fungi (Ni M, Yu JH. 2007). The type of mold encountered in this experiment was Rhizopus stolonifer, which is black bread mold. The bread samples used were placed in seven different types of environments. The samples were observed in their environments for approximately three weeks. Table 1.1 shows the amounts of mold growth on the different bread samples in the different environments. Figure 1.1 shows that the bread samples placed in refrigeration, salt, sugar, and vinegar did not have any mold growth, while the control and the samples placed in water and darkness had rapid mold growth. Growing and observing mold is important because it can help us discover new uses for mold. For instance, in 1928, Sir Alexander Fleming was able to observe that the mold Penicillin could destroy some types of bacterium (Thomas Scientific, 2006). So the question still remains as to why there was a sudden drastic increase in mold growth for the darkness variable. Mold needs like to grow. Mold runs on a cycle in which it sends out spores to grow at a certain point each day (Science News 1995). Simply exposing the darkness variable to a few minutes of light every time we took measurement could have reset the mold's biological clock, resulting in the growth of mold. The reason why the mold growth on the control, darkness and water variables plateaus is because there was no more bread for the mold to absorb. Therefore, if left to continue, the mold would have continued to grow and grown upon itself. The possible sources of error which could have occurred would be not putting enough water in the water variable, or exposing the dark variable to light for too long. There do not seem to be any inconsistencies in my data. The purpose of the control was to have a standard to compare the other variables to. Other variables which could have been tested could be jelly or maybe some type of dairy product. I think that jelly would take longer to show mold growth than plain bread however, because jelly has such a high sugar concentration, which we already discussed is a preservative. References
Borst, Daryll. 2007. Laboratory Studies in Honors General Biology. ED 1. Quinnipiac University. Laboratory Exercise 1.
Campbell, Neil A., and Jane B. Reece. 2005. Biology. Ed. Beth Wilbur. 7th ed. San Francisco: Benjamin Cummings, 2005. 611-623. Campbell, Neil A., and Jane B. Reece. 2005. Biology. Ed. Beth Wilbur. 7th ed CD-ROM and website. San Francisco: Benjamin Cummings, 2005. http://wps.aw.com/bc_campbell_biology_7/0,9854,1705913-,00.html Jung HJ. 2007. S-Phase Accumulation of Candida albicans by Anticandidal Effect of Amentoflavone Isolated from Selaginella tamariscina. http://www.ncbi.nlm.nih.gov/sites/entrez? Db=pubmed&Cmd=ShowDetailView&TermToSearch=17917274&ordinalpos=5&itool=EntrezS ystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum Ni M, Yu JH. 2007. A Novel Regulator Couples Sporogenesis and Trehalose Biogenesis in Aspergillus nidulans. http://www.ncbi.nlm.nih.gov/sites/entrez? Db=pubmed&Cmd=ShowDetailView&TermToSearch=17912349&ordinalpos=8&itool=EntrezS ystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum Science News. 1995. Vol. 148 Issue 7, p111. Science Reference Center. Retrieved from the World Wide Web: http://search.ebscohost.com/login.aspx? direct=true&db=sch&AN=9508292581&site=ehost-live Thomas Scientific. 2006. Century of Science. Retrieved from the World Wide Web: http://scientific.thomson.com/media/presentrep/facts/centuryofscience.pdf ...
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