A kinetic study on the fermentation of skim milk with Lactobacillus plantarum BS immobilized in gelatin for the production of probiotic drink

Date

4-2010

Degree

Bachelor of Science in Chemical Engineering

College

College of Engineering and Agro-Industrial Technology (CEAT)

Adviser/Committee Chair

Marilyn C. Del Barrio

Co-adviser

Francisco B. Elegado

Committee Member

Monet Concepcion C. Magnuyon, Ma. Cristina V. Mahilum

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Abstract

Lactobacillus plantarum BS was cultured and successfully immobilized using gelatin as medium. The gelatin cubes produced were yellow in color and proved to be mechanically weak and non-resistant to acidic environment. The growth kinetics of gelatin-immobilized Lactobacillus plantarum BS was also investigated at 8, 10, and 12% (w/v) skim milk as substrates. Batch fermentation was done, setting the temperature constant at 37C and agitation speed at 100 rpm. Total Sugar consumption, biomass concentration, titratable acidity, pH and viability of immobilized cells during storage were determined. Fermentation of Skim Milk substrate reached maximum growth of 6.5E+07 CFU/ml, 6.0E+07 CFU/ml and 6.1E+07 CFU/mL for 8, 10 and 12% (w/v) respectively. Exponential phase ended at the 6th hour. Statistically, biomass production was highest in 8%, followed by 12% and the least in 10% concentration. It was found out that total sugar concentration was observed to decrease as fermentation progressed, suggesting the utilization of the microorganism of the substrate for its growth. Substrate consumption was the highest in 8%, which can be attributed to the high amounts of biomass produced in the said concentration as compared to 10% and 12% (w/v). The drop in pH was minimal for the first 8 hours of fermentation for all substrate concentrations, which was due to the buffering capacity of milk. However, pH drop was steepest in the 8% concentration. This was attributed to the higher amounts of biomass produced in the 8% concentration which utilized substrate for their growth and in turn produce lactic acid, which caused the drop in pH. Furthermore, pH drop between the 10% and 12% were not significantly different. Titratable acidity was also measured throughout fermentation and was found out to decrease the longer the fermentation time which also corresponded to the drop in pH. However, improvements regarding the measurement of titratable acidity are suggested. Gelatin-immobilized Lactobacillus plantarum BS was also tested for viability during a 4- week storage period. For immobilized cells, the numbers of viable cells remaining inside the beads were observed to drop to 61% of the original amount after the 1st week. After the succeeding weeks, the viable cells remaining were 58%, 45.5% and 56% for the 2nd, 3rd and 4th week respectively. For free cell, the viable cells were reduced to 5% after the 1st week and 2.4% after the 2nd week. It was statistically found out that gelatin-immobilized cells were more viable compared to free cell in a phosphate buffer during the 4-week storage, suggesting that immobilizing Lactobacillus plantarum BS in gelatin would help improve cell viability during storage. The growth of gelatin-immobilized Lactobacillus plantarum BS was best described by the Moser Model yielding a 0.3556 hr-1 and a Ks value equal to 3.2E+7 g/mL.

Language

English

Location

UPLB College of Engineering and Agro-Industrial Technology

Document Type

Thesis

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