Optimization of production and characterization of exopolysaccharide from lactic acid bacteria / Ivy Capangpangan Emnace ; Erlinda I. Dizon, chair, advisory committee.

Date

7-2015

Abstract

This study aimed to screen the best exopolysaccharide (EPS) producing lactic acid bacteria (LAB) (Lactobacillus delbrueckii ssp. lactis, Lactobacillus rhamnosus NBRC 3425 and Weisella paramesenteroides), optimize growth conditions affecting EPS yield and characterize the crude EPS. The screening for the highest EPS production was estimated using phenol-sufuric acid assay. The optimum growth conditions for EPS production: incubation temperature (37% deg C), initial pH (6.0), and carbon source (2% glucose) was carried out using the Central Composite Design (CCD) of the Response Surface Methodology (RSM). Quantitative analysis of estimated EPS revealed that L. rhamnosus NBRC 3425 produced the highest yield (0.1355 g/L) among the three screened LAB. Optimization study revealed that the viable count of L. rhamnosus NBRC 3425 grown in semi- defined medium was maximum at 32.3 deg C, pH of 6.46, and at any amount of glucose from 1 to 3% is linearly affected by incubation temperature. The temperature, initial pH and their interaction had significant effect on the variations of the final pH of the fermented medium. Titratable acidity was significantly affected by temperature and carbon source (linear and quadratic), initial pH (quadratic), and the interaction of initial pH and temperature. The total soluble solids (TTS) was highly affected by the linear attributes of temperature and amount of carbon source and quadratically by initial pH. The combination of temperature andinitial pH that harness maximum total sugar production is found at a temperature of 35.76 deg C and initial pH of 4.93. When the amount of glucose is not less than 2.3% (wt/vol) the lowest possible total sugar harvest is 0.1111 g/L. High biomass readings were found at temperature near 37 deg C and glucose level of 2.0%. The obtained optimal growth condition combination of independent variables was 37deg C, 2% and 6.0 for incubation temperature, carbon source and initial pH, respectively. The FTIR spectrum of crude EPS produced by L. rhamnosus NBRC 3425 revealed the presence of hydroxyl (OH) groups of carbohydrate and carbonyl group (C=O). SEM analysis showed that the crude EPS sample exhibits the presence of pores and spaces between particles. Further visualization by TEM of the L. rhamnosus NBRC 3425 cells revealed a clear cell wall or halo surrounding the bacterial surface, confirming the presence of exopolysaccharide. Atomic force microscopy (AF M) of crude EPS at a concentration of 10 mug/ml revealed spike shaped lumps with an average size of 17.81 +-.89 nm.

Document Type

Dissertation

Degree

Doctor of Philosophy in Food Science

College

Graduate School (GS)

Adviser/Committee Chair

Erlina I. Dizon

Committee Member

Ernesto V. Carpio, Francisco B. Elegado, Virginia L. Barraquio, Erlina I. Dizon

Language

English

LC Subject

Lactic acid bacteria, Polysaccharides, Microbial exopolysaccharides, Food Science Food Science Cluster

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 996 2015 F61 E46

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