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The selectivity of nutrient broth-virgin coconut oil for gram-negative organisms.


Lutherine Mariz A. Balagonsa,
Manuel Christopher M. Hermoso,
Maika Lalaine I. Manuel,
Silvino Rey H. Pino,
Arlene C. Rabilas,
Josiebel  S. Reynes,
Ivy Sharon B. Roma,
Wilton Yves T. Tejero,
Michelle C. Varona,
Jubeelyne F. Gernale

Related Institution

College of Allied Medical Sciences - Medical Technology Department - Cebu Doctors' University

Publication Information

Publication Type
Thesis Degree
Medical Technology
Publication Date
April 2015


                  Virgin coconut oil is defined as oil obtained from the fresh, mature kernel of the coconut by mechanical or natural means. It has antimicrobial activity which is due to the presence of fatty acids namely lauric acid and monolaurin that attacks the plasma membrane lipid bilayer of a microorganism. This study aims to investigate the selectivity of virgin coconut oil as it is incorporated into an enrichment medium which is the nutrient broth and then extracted into different concentrations namely 10%, 25%, 50%, 75%, and 100%. Broth dilution test was then performed by first inoculating Gram-negative bacteria namely Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa and Gram-positive bacteria namely Staphylococcus aureus and Streptococcus haemolyticus to the Nutrient Broth-Virgin Coconut Oil to determine the growth by the presence of turbidity. Gram-staining was done to confirm growth of bacteria that showed positive turbid results in the different concentrations of Nutrient Broth-Virgin Coconut Oil. Biochemical Testing was also executed to identify the correct specie of the organisms that showed growth in the Nutrient Broth-Virgin Coconut Oil.

              Growth was observed in Nutrient Broth-Virgin Coconut Oil as indicated by turbidity in 10% and 25% concentrations for all Gram-negative bacteria. For Gram-positive Staphylococcus aureus, turbidity was only observed in the 10% concentration while Streptococcus haemolyticus did not grow in all concentrations. Both Gram-negative and Gram-positive bacteria are inhibited at 100% concentration. Gram-staining reactions showed pink to red bacilli rods that are correct for Gram-negative bacteria while purple to violet round cocci for Gram-positive bacteria. The inoculation of test organisms for 50% and 75% concentrations of Nutrient Broth-Virgin Coconut Oil was not applicable because of the formation of a milky emulsion that is already turbid. The turbid results that are obtained were then subjected to culture for the isolation of pure colonies by using the Four Quadrant Streak Method. The pure colonies were then used for biochemical testing to confirm the specie of the Gram-negative bacteria that were isolated.

               Nutrient Broth­-Virgin Coconut Oil was selective to Gram-negative bacteria. At 25% concentration, the Gram-negative bacteria namely Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa showed turbid results as it inhibited the growth of the Gram-positive bacterium Staphylococcus aureus. There was no growth observed for Streptococcus haemolyticus in all concentrations of Nutrient Broth-Virgin Coconut Oil. In a much higher concentration which is 100%, both Gram-negative and Gram-positive bacteria were inhibited. It is recommended to determine another procedure of emulsifying virgin coconut oil in order to produce 50% and 75% concentration of Nutrient Broth-Virgin Coconut Oil and to use another surfactant other than Tween 20 to make a better emulsion with virgin coconut oil. It is also recommended to identify other microorganisms that Nutrient Broth-Virgin Coconut Oil can selectively grow or inhibit and to determine another growth medium other than nutrient broth that can be mixed with virgin coconut oil.


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