Changes in some molecular properties of synthetic and natural melanoidins after decolorization by Bacillus subtilis

Louie B. Rico

Date

10-1996

Degree

Bachelor of Science in Chemistry

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Ernesto J Del Rosario

Abstract

RICO, LOUIE BANTA. College of Arts and Sciences, University of the Philippines Los Banos, October 1996. Changes in Some Molecular Properties of Synthetic and Natural Melanoidins After Decolorization by Bacillus subtilis.

Adviser: Dr. Ernesto J. Del Rosario

Synthetic melanoidin prepared from equimolar concentrations of glucose and glycine, and natural melanoidin from alcohol distillery biodigester effluent were decolorized by an isolate of Bacillus subtilis. The isolate decolorized 71.87 ± 1.31% of synthetic melanoidin with 1.7 x 109 cfu/rnL inoculum size while 61.06 ± 0.79% of natural melanoidin was decolorized with 2.9 x 109 cfu/ml, inoculum size, under optimal conditions after 8 days of fermentation. The MDA values for both melanoidins were found to be significantly different at the 1% level of significance.

Gel chromatography through Sephadex G-100 showed a decrease in average molecular weight (MW) from 42.46 ± 0.42 to 37.74 ± 0.38 1dD of synthetic melanoidin and from 35.58 ± 0.36 to 33.54 ± 0.34 IcD of natural melanoidin, after microbial action. The intrinsic viscosity, [i], also decreased after microbial decolorization. Synthetic melanoidin had [n] values of 19.77 t 0.02 and 17.16 ± 0.19 (g/mL)"i for the control and decolorized solution, respectively. The [TA values of natural melanoidin before and after decolorization were 18.46 ± 0.03 and 16.96 ± 0.07 (g/mL)"1, respectively. The [n] values for the controls and decolorized samples of both melanoidins were found to be significantly different at the 1% level of significance.

Comparison of the UV-Visible spectra of controls and decolorized solutions of both melanoidins showed increased absorbance at 220-380 nm and decreased at >380 nm. Infrared spectroscopy of the microbially-treated synthetic melanoidin revealed decreased intensity of C=0 and C=C absorption relative to 0-H, and the appearance of absorption attributable to the alkoxy (C-0) functional group. The results suggest an oxidative degradation of both melanoidins caused by oxidase enzyme(s) secreted by the microorganism.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

Thesis

Document Type

Thesis

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