Effect Of Starch Acetylation On Bioplastics- Degrading Microorganisms: A Pointer To Assessing Biodegradation

The substitution of the hydroxyl groups with acetyl groups into starch moiety to increase hydrophobicity is geared toward enhancing the functional properties of starch for bioplastics production. The fear for reduced biodegradability of the products however, informed the isolation and identification of starch acetate based-bioplastics degraders in soil as a pointer for acetylation effect on degradation. Native starch and starch acetates from cassava, maize and potato were used for the production of bioplastics according to the composition of 45%, 60%, 75% and 90% respectively. Bioplastics measuring 2.5cm x 1.5cm x 0.5cm from each bioplastics composition was buried. Rate of degradation was estimated at intervals of 1week. Soil from the decomposed bioplastics were placed on nutrient and potato dextrose agars for bacteria and fungi isolation and incubated at 300C for 2hrs. Discrete colonies were transferred to nutrient and potato dextrose agars for 24 and 72hrs to produce pure cultures of bacteria and fungi. Gram staining and biochemical tests were done while fungi mycelia were stained with lactophenol blue for microscopy. Our results revealed that there was significant effect (P < 0.05) of starch acetylation on the degradation of bioplastics. Pseudomonas spp, Bacillus anthrax, Corynebacterium diphtheria, Micrococcus, Klebsiella spp and Clostridium spp were bacteria species isolated while the isolated fungi species were Aspergillus niger, Mucor spp, Alternaria spp, Chanophora cucurbitarum during the preliminary soil analysis. After the burial test, bacteria identified as colonizing the bioplastics were as follows; Pseudomonas spp, Bacillus anthrax, Micrococcus, Klebsiella spp and Clostridium spp while Aspergillus niger, Mucor spp, Alternaria spp, Chanophora cucurbitarum were the identified fungi and implicated for the degradation, which was confirmed through in vitro. The delayed degradation observed in our result may not mean jettisoning the idea of acetylating starch, especially in planta of starch-producing plant for bioplastics production comparing the degradation problems of synthetic plastics, which had led to finding alternatives. Our results explicitly suggest that though using acetylated starch for bioplastics production might have a little degradation problem, the microorganisms isolated had the capacity to degrade them in a very short interval of weeks.