Biosynthesis and characterization of polyhydroxyalkanoates copolymers produced by pseudomonas putida bet001 isolated from palm oil mill effluent

The biosynthesis and characterization of medium chain length poly-3-hydroxyalkanoates (mcl-PHA) produced by Pseudomonas putida Bet001 isolated from palm oil mill effluent was studied. The biosynthesis of mcl-PHA in this newly isolated microorganism follows a growth-associated trend. Mcl-PHA accumulation ranging from 49.7 to 68.9% on cell dry weight (CDW) basis were observed when fatty acids ranging from octanoic acid (C8:0) to oleic acid (C18:1) were used as sole carbon and energy source. Molecular weight of the polymer was found to be ranging from 55.7 to 77.7 kDa. Depending on the type of fatty acid used, the 1H NMR and GCMSMS analyses of the chiral polymer showed a composition of even and odd carbon atom chain with monomer length of C4 to C14 with C8 and C10 as the principal monomers. No unsaturated monomer was detected. Thermo-chemical analyses showed the accumulated PHA to be semi-crystalline polymer with good thermal stability, having a thermal degradation temperature (Td) of 264.6 to 318.8 (60.2) oC, melting temperature (Tm) of 43.(60.2) oC, glass transition temperature (Tg) of 21.0 (60.2) oC and apparent melting enthalpy of fusion (DHf) of 100.9 (60.1) J g21

Poly-3-hydroxyalkanoates-co-polyethylene Glycol Methacrylate Copolymers for pH Responsive and Shape Memory Hydrogel

Multifunctional hydrogels combining the capabilities of cellular pH responsiveness and shape memory, are highly promising for the realization of smart membrane filters, controlled drug released devices, and functional tissue-engineering scaffolds. In this study, lipase was used to catalyze the synthesis of medium-chain-length poly-3-hydroxyalkanoates-co-polyethylene glycol methacrylate (PHA-PEGMA) macromer, which was used to prepare pH-responsive and shape memory hydrogel via free radical polymerization. Increasing the PEGMA fraction from 10 to 50% (mass) resulted in increased thermal degradation temperature (T-d) from 430 to 470 degrees C. Highest lower critical solution temperature of 37 degrees C was obtained in hydrogel with 50% PEGMA fraction. The change in PEGMA fraction was also found to highly influence the hydrogel's hydration rate (r) from 2.8 x 10(-5) to 7.6 x 10(-5) mL.s(-1). The hydrogel's equilibrium weight swelling ratio (q(e)), protein release and its diffusion coefficient (D-m) were all found to be pH dependent. Increasing the phosphate buffer pH from 2.4 to 13 resulted in increased q(e) from 2 to 16 corresponding to the enlarging of network pore size (xi) from 150 to 586 nm. Different types of crosslinker for the hydrogel influenced its flexibility and ductility. (C) 2014 Wiley Periodicals, Inc

Single-step lipase-catalyzed functionalization of medium-chain-length polyhydroxyalkanoates

BACKGROUND: Functionalization of aliphatic biopolymers such as bacterial polyhydroxyalkanoates (PHA) using biologically active hydrophilic moieties like sugars helps to improve the hydrophilicity and biodegradability of the biomaterial. RESULTS:Theeffects of reaction variables reaction time, temperature,enzyme concentration and substrate ratio on reaction rate and yield in the synthesis of poly(1’-O-3-hydroxyacyl-sucrose) using Candida antarctica lipase B (EC 3.1.1.3)were studied. Using H2O2 as micro-initiator, enzyme-mediated synthesis yielded reaction rate, vapp of 0.076 x 10−5 mol L−1 s−1. The biodegradability of the functionalized polymer was observed to increase by 1.5 fold compared with the non-functionalized material apart from showing better compostability. Increasing the reaction temperature (>50◦C), enzyme concentration (>15 g L−1) and reactant ratio (w/w) of sucrose:PHA (>2) did not increase further the rate or yield. The sucrose-functionalized mcl-PHAwas characterized with respect to the non-functionalized material. CONCLUSIONS: Novozym 435 can be used effectively to synthesize poly(1’-O-3-hydroxyacyl sucrose) in micro-aqueous medium bypassing the need for chemo-synthetic steps. The synthesized biomaterials have potential applications in biomedical and industrial niche

Enzymatic synthesis of 6-O-glucosyl-poly(3-hydroxyalkanoate) in organic solvents and their binary mixture

The effects of organic solvents and their binary mixture in the glucose functionalization of bacterial poly- 3-hydroxyalkanoates catalyzed by LecitaseTM Ultra were studied. Equal volume binary mixture of DMSO and chloroform with moderate polarity was more effective for the enzyme catalyzed synthesis of the carbohydrate polymer at≈38.2 (±0.8)% reactant conversion as compared to the mono-phasic and other binary solvents studied. The apparent reaction rate constant as a function of medium water activity (aw)was observed to increase with increasing solvent polarity, with optimum aw of 0.2, 0.4 and 0.7 (±0.1) observed in hydrophilic DMSO, binary mixture DMSO:isooctane and hydrophobic isooctane, respectively.Molecular sieve loading between 13 to 15 g L−1 (±0.2) and reaction temperature between 40 to 50 ◦C were found optimal. Functionalized PHA polymer showed potential characteristics and biodegradability

Ultrasound-assisted enzymatic synthesis of poly-ε -caprolactone: kinetic behavior and reactor design

Lipase-mediated, ultrasound-assisted synthesis of poly-ε-caprolactone was investigated. It was found that ultrasound irradiation helped to improve the rate constant of poly-ε-caprolactone chain propagation (kp) at high initial monomer (ε-caprolactone) concentration. The enhancement of kp ranged from 34% to 46% at 22.5– 18.0 M initial monomer concentration, respectively. In a system proned to time-dependent mass-transfer limitation due to polymer chain extension, the acoustic effects could have also allowed the reaction to continue longer compared to non-sonicated process until it became impossible at highly elevated reaction mixture viscosity (>2,000 times increase from initial viscosity). Consequently, it also helped to improve monomer conversion. In a continuous flow polymerization system, a plug flow reactor system is recommended due to its lowest volume for maximum conversion compared to a continuously stirred tank reactor system

Ultrasound assisted lipase catalyzed synthesis of poly-6-hydroxyhexanoate

Ultrasonic irradiation greatly improved the Candida antarctica lipase B mediated ring opening polymerization of e-caprolactone to poly-6-hydroxyhexanoate in the ionic liquid 1-ethyl-3-methylimidazolium tetraflouroborate. Compared to the conventional nonsonicated reaction, sonication improved the monomer conversion by 63% and afforded a polymer product of a narrower molecular weight distribution and a higher degree of crystallinity. Under sonication, the polydispersity index of the product was 1.44 compared to a value of 2.55 for the product of the conventional reaction. With sonication, nearly 75% of the monomer was converted to product, but the conversion was only 16% for the reaction carried out conventionally. Compared to conventional operation, sonication enhanced the rate of polymer propagation by >2-fold and the turnover number of the lipase by >3-fold

Recent advances in the production, recovery and applications of polyhydroxyalkanoates

Polyhydroxyalkanoates (PHAs) are biodegradable and biocompatible polyesters that can potentially replace certain plastics derived from petroleum. PHAs can be produced using a combination of renewable feedstocks and biological methods. Native and recombinant microorganisms have been generally used for making PHAs via fermentation processes. As much as 90 % of the microbial dry mass may accumulate as PHAs. A range of PHAs has been produced using fermentation methods, including copolymers and block copolymers. Alternative production schemes based on genetically modified plants are becoming established and may become the preferred route for producing certain PHAs. Production in plants is likely to be inexpensive compared to production by fermentation, but it does not appear to be as versatile as microbial synthesis in terms of the range of products that may be generated. Cellfree enzymatic production of PHAs in vitro is receiving increasing attention and may become the preferred route to some specialty products. This review discusses the recent advances in production of polyhydroxyalkanoates by the various methods. Methods of recovering the polymer from microbial biomass are reviewed. Established and emerging applications of PHAs are discussed

Lipase mediated synthesis of sugar fatty acid esters

This review is concerned with lipase catalyzed synthesis of sugar fatty acid esters in water immiscible organic solvents. Sugar esters are widely used nonionic and nontoxic biosurfactants. Certain sugar esters inhibit microbial growth and have other activities. Lipase mediated synthesis has important advantages over conventional chemical synthesis of sugar esters. Lipase catalyzed synthesis is typically carried out in organic solvents having a low water activity to drive the reaction towards synthesis instead of towards ester hydrolysis. The impact of the various reaction conditions on enzymatic synthesis of sugar esters in nonaqueous media is discussed. Considered in particular are the solvent effects; the effects of water activity; the influence of the nature and concentration of the reactants (sugars and fatty acids); the influence of temperature; and the effects associated with the specific nature of the lipase catalyst used