Bacterial synthesis of poly(hydroxybutyrate- co-hydroxyvalerate) using carbohydrate-rich mahua (Madhuca sp.) flowers.
OBJECTIVE
The objective of the present work was to utilize an unrefined natural substrate namely mahua (Madhuca sp.) flowers, as a carbon source for the production of bacterial polyhydroxyalkanoate (PHA) copolymer by Bacillus sp-256.


RESULTS
In the present work, three bacterial strains were tested for PHA production on mahua flower extract (to impart 20 g l(-1) sugar) amongst which, Bacillus sp-256 produced higher concentration of PHA in its biomass (51%) compared with Rhizobium meliloti (31%) or Sphingomonas sp (22%). Biosynthesis of poly(hydroxybutyrate-co-hydroxyvalerate) - P(HB-co-HV)--of 90 : 10 mol% by Bacillus sp-256 was observed by gas chromatographic analysis of the polymer. Major component of the flower is sugars (57% on dry weight basis) and additionally it also contains proteins, vitamins, organic acids and essential oils. The bacterium utilized malic acid present in the substrate as a co-carbon source for the copolymer production. The flowers could be used in the form of aqueous extract or as whole flowers. PHA content of biomass (%) and yield (g l(-1)) in a 3.0-l stirred tank fermentor after 30 h of fermentation under constant pH (7) and dissolved oxygen content (40%) were 54% and 2.7 g l(-1), respectively. Corresponding yields for control fermentation with sucrose as carbon source were 52% and 2.5 g l(-1). The polymer was characterized by proton NMR.


CONCLUSIONS
Utilization of mahua flowers, a natural substrate for bacterial fermentation aimed at PHA production, had additional advantage, as the sugars and organic acids present in the flowers were metabolized by Bacillus sp-256 to synthesize P(HB-co-HV) copolymer.


CONCLUSIONS
Literature reports on utilization of suitable cheaper natural substrate for PHA copolymer production is scanty. Mahua flowers used in the present experiment is a cheaper carbon substrate compared with several commercial substrates and it is rich in main carbon as well as co-carbon sources that can be utilized by bacteria for PHA copolymer production.
Anil Kumar
P K
PK
Department of Food Microbiology, Central Food Technological Research Institute, Mysore, Karnataka, India.
Shamala
T R
TR
Kshama
L
L
Prakash
M H
MH
Joshi
G J
GJ
Chandrashekar
A
A
Latha Kumari
K S
KS
Divyashree
M S
MS
D001407:Bacillus / Q000254:growth & development / Q000378:metabolism*; D018533:Biomass; D019149:Bioreactors; D002241:Carbohydrates / Q000032:analysis; D003470:Culture Media; D005285:Fermentation; D035264:Flowers; D032128:Madhuca / Q000378:metabolism*; D008293:Malates / Q000494:pharmacology; D010936:Plant Extracts / Q000494:pharmacology; D011091:Polyesters / Q000378:metabolism*; D019802:Succinic Acid / Q000494:pharmacology; D000094122:Polyhydroxybutyrates
D002241:Carbohydrates; D003470:Culture Media; D008293:Malates; D010936:Plant Extracts; D011091:Polyesters; D019802:Succinic Acid; C052620:poly(3-hydroxybutyrate)-co-(3-hydroxyvalerate); D000094122:Polyhydroxybutyrates; C030298:malic acid