Microbiological and molecular characterization of cellulose producing Gluconacetobacter sp

Biodegradable polymers are in great demand due to their environmental
friendly nature. Polysaccharides from microbial source are most commonly
used. Microbial polysaccharides are produced by various genera of bacteria
having wide variety of applications. The production of bacterial cellulose (BC)
is a characteristic feature of Gluconacetobacter sp. In a liquid medium
Gluconacetobacter produces BC in the form of floating pellicle comprising of
cellulose, entrapped cells and other media ingredients. In the present work
BC producing bacterium was isolated, characterized and identified. Based on
morphological, biochemical and molecular methods - the isolate was identified
as Gluconacetobacter hansenii. The purified BC film produced by native
isolate was characterized for its structural and molecular properties by GC,
scanning electron microscopy, FT-IR, 13C NMR. The results indicate BC to be
made up of only glucose monomers. Physico-mechanical, barrier properties,
thermal characteristics of melt, decomposition were analysed by differential
scanning caloriemetry and thermal stability by thermo gravimetric analysis.
The nutritional and cultural conditions for the enhanced production of BC were
optimized from the native isolate G. hansenii UAC09. To economize the BC
production, agro wastes like coffee cherry husk extract, and molasses as
carbon source and corn steep liquor as nitrogen source were exploited. High
yield of BC was achieved from a combination of coffee cherry husk extract
and 8% corn steep liquor. Response surface methodology was used for
optimization of media components. To understand the utilization of pectin and
polyphenols from CCH by G. hansenii UAC09, production aspects of
pectinases, tannase and polyphenol oxidase enzymes were studied.
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Experiments were carried out to understand the changes in sugars and
polyphenols during the course of fermentation in the coffee cherry husk
extract culture broth and cellulose produced. For the improvement of
packaging properties, the BC films were coated with vinyl resin - carboxyl
modified vinyl chloride (VMCH, food grade) and its properties were studied.
The studies conclude that native isolate G. hansenii UAC09 has a high
potency to produce BC. The BC produced exhibited good physico-mechanical
properties and after coating a fair sealing property.