Isolation of Polyhydroxybutyrate (PHB) Producing Bacteria, Optimization of Culture Conditions for PHB production, Extraction and Characterization of PHB

Abstract

Polyhydroxybutyrates (PHBs) are energy reserves synthesized by different micro-organisms such as Alcaligenes, Pseudomonas, Staphylococcus, Algae, in excess of carbon and limitation of nutrients like nitrogen. These biopolymers are suitable alternate to synthetic carbon-based polymers. However, the high production cost limits their commercialization. The aim of this study was thus, focused on optimization of culture condition for maximum PHB production in an attempt to reduce the production cost. The micro-organisms for this purpose were isolated from 4 different soil samples and screened for PHB production. Culture conditions for these organisms were optimized by changing the parameters, viz., incubation time, pH, carbon source and NaCl concentration. Thus, optimized culture condition was used to culture the isolates for extraction of PHB and its analysis. The extracted compounds on FTIR-analysis gave characteristic C=O peak of PHB, thus, confirming the seven isolates to be PHB producers. Results for optimized parameters for the isolated PHB positive species showed that synthesis of PHB was maximum at 48 hours i.e. during the early stages of stationary phase. However, different isolates favored different culture conditions. Highest PHB accumulation and growth of isolates were seen at pH 7 and 9. Similarly, it was observed that glucose was favored by 4 isolates and sucrose was favored by 3 isolates. Interestingly, NaCl concentration did not cause significant effect on neither the bacterial growth nor the PHB production. During the extraction of PHB from the optimized culture conditions, extraction of PHB from broth gave significant yield than that from agar. A good PHB yield from broth amounting to 36.41% and 34.59% was observed for Bacillus pasteurii and Micrococcus luteus respectively, showing a potential for their exploitation in industrial PHB production. At optimized conditions, 7 isolates exhibited significant PHB yields, thus showing a potential for further exploitation.

Bioplastic (poly-3-hydroxybutyrate) production by the marine bacterium Pseudodonghicola xiamenensis through date syrup valorization and structural assessment of the biopolymer

“…Various optimal fermentation periods have been mentioned for the production of PHB at the beginning of the stationary phase of growth depending on bacterial strains. Some reports refer to 48 h of incubation as being optimal for PHB production by Bacillus pasteurii and Micrococcus luteus, affording maximum PHB yields of 36.41% and 34.59%, respectively 41 , while for Rhizobium etli www.nature.com/scientificreports www.nature.com/scientificreports/ E1 and Pseudomonas stutzeri E114, PHB yields of 81.80% and 83.02%, respectively, were achieved 42 . In addition, Bacillus spp.…”

“…The results obtained were highly comparable with the data for marine Bacillus megaterium MSBN04, and high PHB production (56.81%) with the maximum PHB yield (8.637 mg/ g of the substrate) was achieved at pH 7.5 and drastically reduced at acidic pH compared to alkaline pH 24 . The production of PHB was supported at pH 7 to 9 by the marine bacteria Vibrio azureus 17 , B. pasteurii and M. luteus 41 . Additionally, the highest PHB production (3.2-6.8 g/L) was observed at pH 7.0-7.5 for R. etli, P. stutzeri, and Bacillus sp 42,43 .…”

“…In the present study, the values of the FTIR absorption bands of the carbonyl group, -OH group, -C-H group, and -CH 2 and -CH 3 groups were related to values reported in recent studies [53][54][55][56] . One of the most common chemical groups in all types of PHAs is the carbonyl group (C = O) 41,43 . The strong band at 1724 cm −1 for carbonyl stretching of the ester group of the extracted PHB is analogous to that for the standard PHB and the peak of the C = O group for PHB from Bacillus cereus 31,43 .…”

Biodegradable Plastic (Phb) From Bacteria Collected From Gopalpur Beach, Bhubaneswar

“…Despite these interesting properties, the industrial production of PHB remains not well established owing to its high production cost. This high costing has made it unable to compete with conventional cost-effective plastics in the commercial market [8]. The PHB content and its composition are influenced mainly by the strain of the microorganism, the type of substrate employed and its concentration, and other growth conditions such as pH, time and temperature [8].…”

“…This high costing has made it unable to compete with conventional cost-effective plastics in the commercial market [8]. The PHB content and its composition are influenced mainly by the strain of the microorganism, the type of substrate employed and its concentration, and other growth conditions such as pH, time and temperature [8]. This study emphasises on isolation and characterization of PHB producing bacteria from easily accessible source i.e., contaminated water samples.…”