Mechanical Properties, Crystallization and Biodegradation Behavior of the Polylactide/Poly(3-hydroxybutyrate-co-4-hydroxybutyrate)/ Poly(butylene adipate-co-terephthalate) Blown Films

Polactide(PLA),poly(3-hydroxybutyrate-co-4-hydroxybutyrate)(P(3HB-CO-4HB)),and poly(butylene adipate co-terephthalate)(PBAT)ternary blends were prepared by extrusion blending.The biodegradable PLA/P(3HB-co 4HB)/PBAT films were successfully obtained by using blown films technique.Excellnt siffness-toughness balance was achieved for 55/10/35 PLA/P(3HB-co 4HB)/PBAT film.The tensile strength reached 33.0 MPa(MD)and 23.5 MPa(TD).the elongation at break exceeded 1309%,and tear strength exceeded 110 kN/m.The Young's modulus as low as about 1800 MPa also met packaging applications.SEM observations revealed rough and long ligaments,indicating that the tear specimens were broken yieldingly.The addition of PBAT elastomers was the main reason for the improved toughness of the film.From DMA and SEM analysis,it was demonstrated that PLA P(3HB co 4HB),and PBAT were prilly compatible.With increasing P(3HB CO-4HB)content,the melt and cold crstallization of PLA was promoted.The enzymatic degradation experiments indicated that the films had good biodegradability.These findings gave important implications for designing and manufacturing biodegradation package of high biological carbon content.

Production of Poly(3-Hydroxybutyrate-co-3-Hydroxyhexanoate) Using Aeromonas hydrophila 4AK4 Grown in Mixed Carbon Source

Aeromonas hydrophila 4AK4 was grown on mixed substrates of soybean oil and lauric acid for the production of polyhydroxyalkanoate copolymer consisting of 3 hydroxybutyrate (3HB) and 3 hydroxyhexanoate (3HHx). A maximal poly(3 hydroxybutyrate co 3 hydroxyhexanoate) (PHBHHx) content of 49.13% in dry cells was obtained in a shake flask culture. PHBHHx of 6.26 g/L was produced in a fermentation experiment over 48 h on a sole carbon source containing 100 g/L soybean oil, while 12.40 g/L PHBHHx was produced on a mixed carbon source containing 80 g/L soybean and 20 g/L lauric acid over the same period of time, resulting in a polyhydroxyalkanoate (PHA) productivity of 0.25 g/(L·h). The results show that mixed carbon sources are suitable for industrialized production of PHBHHx from A. hydrophila 4AK4, as the mixed carbon sources also overcome the foaming problem that occurs when lauric acid is employed as a sole carbon source in PHBHHx production.

Kinetics of Microbial Growth and Synthesis of Poly(3-hydroxybutyrate) Using Fed-batch Culture of Alcaligenes Eutrophus with Phosphorus Limitation

The phosphorus concentration in the culture medium affects the production of poly (3 hydroxybutyrate) (PHB) by Alcaligenes Eutrophus. This investigation shows that the phosphorus concentration in the initial culture medium influences both the residual cell mass and the PHB production. A kinetic model is proposed for the production of PHB in a fedbatch culture of Alcaligenes Eutrophus. The kinetic model is compared with the experimental results and appears to provide an excellent description of the overall fermentation process. A phosphate mass concentration of 45 g/L produced the highest level of dry cell mass concentration (266 g/L), PHB mass concentration (214 g/L), PHB mass content (804%) and PHB productivity (351 g/L·h) so far obtained.

Production of Poly(3-Hydroxybutyrate-co-3-Hydroxyhexanoate) by Aeromonas hydrophila and Recombinant Escherichia coli

Aeromonas hydrophila (A. hydrophila) 4AK4 produced poly(3 hydroxybutyrate co 3 hydroxyhexanoate) (PHBHHx) with an almost constant 3 hydroxyhexanoate (3HHx) content of 10%15% from lauric acid and/or soybean oil. Both A. hydrophila 4AK4 and recombinant Escherichia coli (E. coli) JMU193 (pBH32) produced PHBHHx with controllable 3HHx content when fed lauric acid and another co substrate. With glucose or gluconate as the co substrate, the 3HHx content in the copolyester produced by A. hydrophila 4AK4 was reduced slightly from 12% to 9%. However, the 3HHx content in the copolyester produced by E. coli JMU193 (pBH32) was significantly reduced from 9% to 2% with fructose as the co substrate. These results show that regulation of 3HHx content in PHBHHx can be achieved using genetically engineered E. coli.

Production of Biodegradable Copolyesters and Terpolyesters of Polyhydroxyalkanoates by Alcaligenes latus DSM 1124

Copolyesters of 3 hydroxybutyrate and 4 hydroxybutyrate along with terpolyesters of 3 hydroxybutyrate, 3 hydroxyvalerate and 4 hydroxybutyrate were produced using Alcaligenes latus DSM 1124 in growth media with precursors of 1,4 butanediol or 1,4 butanediol and valerate. Monomer mass fraction w in the copolyesters varied from 63% to 78% 3 hydroxybutyrate and 1 5% to 6 5% 4 hydroxybutyrate (cell dry weight), depending on precursor supplied. w(monomer) in the terpolyesters varied from 55% to 69% 3 hydroxybutyrate, 0 5% to 3 4% 4 hydroxybutyrate and 3 4% to 16% 3 hydroxyvalerate.