Abstract:
The production of terpolymer P(3HB-co-3HV-co-4HB) from the newly isolated strain ; Bacillus sp. BA-019 was investigated. It was found that terpolymer P(3HB-co-3HV-co-4HB) was produced by Bacillus sp. BA-019. By using cane sugar, sucrose and cane-molasses as precursors of 3HB monomer, the result showed that suitable mole fraction of 3HB monomer was synthesized and nearly equal or sucrose. Cane sugar was selected as the precursor of 3HB monomer for further study due to lower cost comparing to that of sucrose. Almost equal mole faction of 3HV monomer were synthesized when sodium propionate and sodium valerate were utilized as precursors of 3HV (26 and 28 mole% respectively). Higher growth of Bacillus sp. BA-019 and terpolymer production were investigated in medium containing propionate comparing to that of valerate. Thus, propionate was utilized as precursor of 3HV monomer. Sodium-4-hydroxybutyrate, 1,4-butanediol and gamma-butyrolactone were studied as the suitable precursor of 4HB monomer. The result showed that the highest mole fraction (18 mole.%) of 4HB was synthesized from Sodium-4-hydroxybutyrate, higher cell mass (2.51 g/l) and higher terpolymer productions (36% by dry cell weight) were obtained comparing to that using gamma-butyrolactone. The mole fraction of each monomer was affected by concentration of its precursor, i.e. higher mole fraction (89 mole%) of 3HB was detected with the highest dry cell weight (3.33 g/l) and terpolymer content (41% by dry cell weight) when sugar concentration was increased. It was observed that increasing of propionate concentration resulting in increasing of 3HV mole fraction and reached maximum as 49 mole%. Suimilarly, higher 4HB mole fraction was determined when sodium 4-hydroxybutyrate concentration increased highest value at 78 mole%. By using two steps cultivation of Bacillus sp. BA-019 with gamma-butyralactone as precursor of 4HB, and 3.40 g/l of cell mass 15 and 32 mole% of 4HB monomer were synthesized with 25 and 50 mM of gamma-butyrolactone, respectively. The physical and mechanical properties of the terpolymer films produced by Bacillus sp. BA-019 were studied. The film of terpolymer with higher 4HB mole fraction i.e. P(3HB-co-17%3HV-co-22%4HB) and the terpolymer film with higher 3HV mole fraction i.e. P(3HB-co-20%3HV-co-14%4HB) showed high percent elongation low Youngs modulus value, T(subscript g) and T(subscript m) values were nearly equal low then resulted in transparency and flexibility. The terpolymer film with highest 3HV mole fraction (81mole%) i.e. P(3HB-co9%3HV-co-10%4HB) exhibited lower value of percent elongation, higher value of Youngs modulus, T(subscript g) and T(subscript m) were higher than those of terpolymer film that contain higher 3HV and 4HB, thus this terpolymer film showed more toughness and brittleness than another two kinds of terpolymer films.