Bacteria from contaminated urban and hilly areas as a source of polyhydroxyalkanoates production

Abstract

Polyhydroxyalkanoates (PHA) production and extraction of different bacterial strains isolated from contaminated urban and hilly areas was conducted. The 30 bacterial isolates were Gram negative and belonged to Pseudomonas, Citrobacter, Klebsiella, Escherichia and Enterobacter genera. Bacterial level of resistance against antibiotics (Penicillin) and heavy metals (zinc, cadmium and copper) was determined. Bacterial isolates from contaminated urban areas were found to be more resistant. The screening for PHA production was done by the Sudan black staining. Among the urban area isolates, U17, U8 and U9 produced highest concentration of PHA (50.4, 40.6 and 37.9%) while in hilly area isolates H8, H6 and H9 showed highest production (45.8, 42.4 and 37.6%) by SDS digestion method. The percentage production was lowered when the extraction was done by sodium hypochlorite digestion method. Selected bacterial strains were optimized for PHA production at different growth conditions that is, pH, temperature and carbon sources. Bacterial isolates U8, U17 and H8 produced maximum amount of PHA 74, 69 and 59%, respectively, at pH 7, 37°C and using cooking oil as carbon source after 72 h. PHA polymerase phaC1/C2 genes were successfully amplified from genomic DNA of three bacterial isolates showing 540 bp DNA fragment which confirmed the presence of phaC1/C2 gene presence. It showed that the corresponding bacterial isolates would have been able to synthesize medium chain length PHA.

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“…One of the major obstacles in producing PHB in recombinant organisms is associated with the instability of the introduced pha genes and loss of the plasmid due to metabolic load of ten limits high yields of the biopolymer [115]. PHA polymerase phaC1/C2 genes were successfully amplified from genomic DNA of three bacterial isolates showing 540 bp DNA fragment which confirmed the presence of phaC1/C2 gene presence [116].…”

Rendimiento de polihidroxialcanoatos (PHA) en microorganismos halófilos aislados de salinas

“…Los PHA pertenecen a un grupo de poliésteres sintetizados por varios microrganismos en forma de gránulos en el citoplasma, siendo utilizados como fuente de carbono y energía en condiciones nutricionales desfavorables (López 2010, Li et al 2016. De esta manera, bacterias productoras de PHA se han aislado en ambientes extremos como las salinas (Guzmán & Guz 2008, Guzmán et al 2017) suelo, agua y sedimentos de habitats con 15 -18% p/v de salinidad (Luque et al 2010), aunque también se han reportado aislados con ambientes contaminados (Razzaq et al 2010, Sánchez et al 2012, residuos industriales (Cardona et al 2013) y suelo rizosférico de cultivos agrícolas (Baca et al 2010, Lisboa & Segura 2010.…”