ABSTRACT
Aims@#Microbiota endogenous to oleaginous plants have attracted special attention in recent years for their biotechnological potentials and applications including the production of biodegradable biopolyester poly(3- hydroxybutyrate) [P(3HB)] as an alternative to thermoplastics. The present study is aimed to screen the endophytic bacteria of selected oleaginous plants such as Arachis hypogaea L., Brassica napus L., Brassica nigra L., Helianthus annuus L., Ricinus communis L. and Sesamum indicum L. for the production of P(3HB). @*Methodology and results@#Bacteria endogenous to the oleaginous plants were isolated from surface sterilized healthy tissues following sterilization with 70% ethanol and 0.5% sodium hypochlorite and screened for P(3HB) production in mineral salts medium. Nile blue A staining method was used for detection of intracellular P(3HB), while the accumulated biopolyester was quantified spectrophotometrically following chemical conversion to chrotonic acid by treating with sulfuric acid. Five potent P(3HB) accumulating isolates have been selected and identified as Cellulosimicrobium cellulans AHS 01 (KX458038), Beijerinckia fluminensis AHR 02 (KX458039), Exiguobacterium acetylicum BNL 103 (KX458037), Bacillus toyonensis BNS 102 (KX458036) and Bacillus cereus RCL 02 (KX458035) based on morphological, physio-biochemical and 16S rDNA sequence analysis. These endogenously growing bacterial isolates accumulated intracellular biopolyester accounting 43-62% of their cell dry weight (CDW) when grown in mineral salts medium supplemented with yeast extract. Intracellular accumulation of P(3HB) by these isolates have also been confirmed by FTIR spectral analysis of lyophilized cell mass and 1HNMR spectra of the extracted polymer. @*Conclusion, significance and impact of study@#These findings, first of its kind point to exploration of endogenous bacterial communities of oil-producing plants as a potential bioresource for production of P(3HB) bioplastics in a sustainable manner.
ABSTRACT
Aims: Poly(3-hydroxybutyrate) [P(3HB)], the microbially produced biodegradable thermoplastics has find wide range of applications in recent years. Development of low cost production strategies utilizing novel organisms is a crucial challenge. Present study is aimed to isolate and screen bacterial endophytes of Brassica nigra L. for the production of P(3HB). Place and Duration of Study: The experiments were performed in the Microbiology Laboratory, Department of Botany, University of Calcutta, Kolkata during 2012-2014. Methodology: Culturable bacterial endophytes were isolated from surface sterilized healthy tissues of B. nigra L. and screened for P(3HB) production in mineral salts medium. The chloroform extracted dried polymer was treated with H2SO4 and quantified spectrophotometrically at 235 nm. Results: About 78% of the bacterial endophytes recovered from surface sterilized B. nigra L. tissues showed different degrees of P(3HB) accumulation. Isolates (9) showing P(3HB) accumulation exceeding 10% of the cell dry weight (CDW) were characterized and tentatively identified as members of Bacillus, Pseudomonas, Xanthomonas, Alcaligenes and Acetobacter. The most potent isolate, BNL 06 identified as Bacillus pumilus BNL 06 (GenBank Accession No. KP202723), accumulated P(3HB) accounting 18% of CDW with an yield of 0.55 g/l. Finally the nature of the polymer was further confirmed by FTIR analysis. Conclusion: Exploration of the endophytic bacterial diversity of B. nigra L. have clearly revealed the potential of Bacillus pumilus BNL 06 for P(3HB) production as an alternative source of thermoplastics.