Bacterial Diversity And Community Structure In Accelerated Biodegradation Test Of PLA/PHB Blends

With the increased applications of plastics, a remarkable amount of them runs into ecosystemas wastes. The biodegradation of PLA/PHB blends by bacterial communities was investigatedwith domesticated strains in this study. After being treated with domesticated strains, themorphology and mechanical property of samples have been compared to that in naturaldegradation. The tendency of tensile strength of samples exposed in tests indicates theirmechanical properties changes and biodegradation effect under nature soil or in lab. Mostsamples, particularly the blend samples degraded in bacterial suspensions, lessened evidentlytheir mechanical properties. The SEM images show the micromorphology of PLA/PHBblends. After56days of being buried under the soil, slight scratches appeared in the fibersurface and fibrous structure of samples just had little damage. These changes indicate thatpolymers material biodegradation processes had occurred slowly. On the contrary After15days of incubation, they all had a lot of pores on the cutis surface and micro-cracks werevisible in the fibrous reticular structure, which were resulted from the degradation of samples.Compared with natural degradation of PLA/PHB blends in soil, the results showed that thedegradation can be accelerated by domesticated strains.To quantify the abundance, diversity and community structure of the domesticatedbacteria communities, DGGE and pyro-sequencing were used to analysis16S rRNA gene.The DGGE profiles showed that there is a high bacterial diversity and a stable functionalcommunity composition in this domesticating process. In total8441sequences obtained inthis test, they can be affiliated to2phyla,3classes and10main genera (>1%of all sequences)The dominant phyla in the domesticated bacteria community were Proteobacteria andFimicutes, representing80.4%and19.4%of total classified sequences (Fig.3.A). At genuslevel,10major genus were sequenced, Citrobacter Salmonella, Lysinibacillus,Escherichia, represented proportion were29.4%,21%,13.99%,11.7%of all sequences(>10%). The main dominant genus group, Klebsiella (6.17%), Pseudomonas (4.73%),Clostridium (3.67%), Aeromonas (2.86%), Enterobacter (1.53%), Cronobacter (1.11%) werecovered more than1%of all sequences. Overall, taken together these data indicated that by probably establishing a new method by using these domesticated strains, it can be helpful forrealizing a short degradation period as well as reaching good biodegradation effect.