Changes in some molecular properties of synthetic and natural melanoidins after decolorization by Aspergillus sp.

Date

10-1997

Degree

Bachelor of Science in Chemistry

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Ernesto J Del Rosario

Abstract

Both dialyzed synthetic melanoidin prepared from equimolar concentrations of glucose and glycine, and natural melanoidin from alcohol distillery biodigester effluent were decoloriied by an isolate of Aspergillus sp.. The fungal isolate decolorized 59.41 ± 0.57 % of synthetic melanoidin and 7L23 f 0.89 % of natural melanoidin with the same inoculum size of 3.8 x 10 9 cfu/ml, under optimal conditions after 8 days of fermentation.

Gel chromatography through Sephadex G-100 showed a decrease in average molecular weight (MW) from 51.10 ± 4.6 to 35.60 ± 3.2 kD of synthetic melanoidin and from 55.53 ± 0.5 to 42.60 4 3.8 kD of natural melanoidin, after microbial action. The intrinsic viscosity, [ti], also decreased after microbial decolorization. Synthetic melanoidin had [ri] values of 22.90 f 0.01 and 18.80 ± 0.09 (g/mL)"' for the control and decolorized solution, respectively.

Comparison of the UV-Vis spectrum of the control and decolorized solution of synthetic melanoidin showed decreased absorbance at >350 nm while that of the natural melanoidins showed decreased absorbance at >280 nm.

The IR spectrum of the microbially-treated synthetic melanoidin revealed decreased intensity of the overlapping C=C and/or C=0 absorption bands relative to 04-I, while that of the natural melanoidin showed an increase in intensity of the overlapping C=C and/or C=0 absorption bands. The results suggest that both melanoidins were probably decolorized through an oxidative degradation caused by oxidase enzyme(s) secreted by the microorganism. However, mycelial adsorption may be a contributory factor for fungal decolorization of melanoidins.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 993.5 1997 C4 P34

Document Type

Thesis

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