Soy Product Effects on Soy Product Effects on Microbial FloraMicrobial Flora

Cameron Herbst

Pittsburgh Central Catholic High School

The ProblemHumans consume many different

things, but how can we know to what extent these things affect our physiology?

A viable question which can be asked is: Do ingested consumables have adverse effects on symbiotic organisms in particular, internal flora?

The ProblemCountless studies have evaluated

the affect of ingested material on human cells and physiology.

Another key component of the body is the natural flora especially those within the alimentary canal. These belong to the families: Clostridium, Fusobacterium, Escherichia, Bacteroides, Eubacterium, and Lactobacillus, among others.

Soy Protein ExtractSoy Protein ExtractIsolated Soy Protein Mix: A highly

refined form of soy protein which contains at least 90% protein on a moisture free basis

Ingredients: Supro® Brand Soy Protein Isolate, Fructose, Natural and Artificial Flavor, FD&C Red 40, Salt, Sucralose

Production and Uses of Soy Protein Production and Uses of Soy Protein IsolatesIsolatesMade from defatted soy flour where most of the fats, carbohydrates, and other non-protein components have been removed

Used to improve texture of meat products, increase dietary protein content, and as an emulsifier

The Dangers of SoyThe Dangers of Soy High levels of estrogen – in baby

formula, equivalent of 5 birth control pills per day

Causes weak thyroid gland which leads to excess fat and heart problems

Possibly linked to an increase of Leukemia cases in children

Suppresses testosterone levels; can be fatal in extreme cases

E.E. colicoli One of the most common forms

of bacteria; Free living, symbiotic or pathogenic

Has been utilized as the most studied prokaryote

There are many of different strains of E. coli, most of which are non-pathogenic. However, there are strains which can produce fatal disease

PurposePurposeTo determine whether soy protein isolate in various concentrations will affect the survivorship of intestinal flora (E. coli)

HypothesisHypothesisNull – Survivorship of E. coli in

varying concentrations of soy protein isolate would not vary significantly from the control.

Alternative – Survivorship of E. coli in varying concentrations of soy protein isolate would vary significantly from the control.

MaterialsMaterials Ethanol (sterilization of instruments) Latex gloves E. coli DH5 alpha Micropipette Tube rack 4 Tubes SDF (per 1 liter) (100mM KH2PO4, 100mM K2HPO4, 10mM MgSO4, 1mM NaCl) Turn table LB agar plates LB media (0.5% yeast extract, 1% tryptone, 1% sodium chloride) Bunsen burner Spreader bar Matches Sterile pipette tips Incubator Vortex Klett spectrophotometer Scale Weigh Boat Supro ® Soy protein isolate

ProcedureProcedure1) E. coli was grown overnight in sterile LB

media.2) A sample of the overnight culture was added

to fresh media in a sterile sidearm flask.3) The culture was placed in an incubator (37°C)

until a density of 50 Klett spectrophotometer units was reached. This represents a cell density of approximately 108 cells/mL.

4) The culture was diluted in sterile dilution fluid to a concentration of approximately 103 cells/mL.

5) Soy protein isolate was weighed into appropriate amounts using the scale and sterile weigh boats.

6) The tubes were prepared as follows:

ProcedureProcedure

Tube #

Soy Protein (g)

E. coli (mL)

SDF (mL)

Final Volume(mL)

Final % Soy Protein

1 0 0.1 9.90 10.0 0

2 0.01 0.1 9.89 10.0 0.1

3 0.1 0.1 9.80 10.0 1.0

4 1.0 0.1 8.90 10.0 10.0

ProcedureProcedure7) The E. coli was allowed to remain

exposed to the soy protein extract for 15 minutes.

8) 100 µL aliquots were removed from the tubes and spread on LB plates. (8 replicates)

9) The plates were incubated at 37 degrees Celsius for 24 hours.

9) The resulting colonies were quantified. Each colony is assumed to have arisen from one cell.

E.E. colicoli Soy Survivorship Soy Survivorship GraphGraph

0.1

10

Dunnett’s TestDunnett’s Test

Variable Comparison

t-value Interpretation

0.1% versus 0% (control)

3.20 Not Significant

1.0% versus 0% (control)

0.359 Significant

10.0% versus 0% (control) 9.13 Significant

α = 0.01T-critical = 3.15

InterpretationInterpretationThere appeared to be a

correlation between the percent concentration of soy protein isolate and cell survivorship. Higher concentrations of soy protein isolate resulted in fewer surviving colonies.

ConclusionConclusionThe null hypothesis was rejected

for the 1% and 10% concentrations of E. coli.

A 10% concentration of Soy protein isolate appeared to greatly reduce E. coli survivorship.

LimitationsLimitationsThis experiment was limited in that pure soy protein was not able to be used.

Plating was not exactly synchronized, which could have resulted in extra time for bacterial replication.

ExtensionsExtensionsIn future studies, synergy of soy effects on other foods could be tested. (2 factor ANOVA)

Varying exposure time of E. coli in the tubes before plating could be tested.

To allow for longer exposure, soy protein could be infused directly into the LB agar.

Cited SourcesCited Sourceshttp://e-colibasics.com/http://www.soyfoods.org/products/soy-

fact-sheets/soy-protein-isolate-fact-sheet

http://www.mercola.com/article/soy/avoid_soy.htm

http://www.soya.be/soy-protein-isolate.php

http://www.karinya.com/soydangers.htm