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

Evaluation of nitrogen sources for growth and production of medium-chain-length poly-(3-Hydroxyalkanoates) from palm kernel oil by pseudomonas putida PGA1

Selected organic and inorganic nitrogen sources were evaluated for growth of Pseudomonas putida PGA1 and its production of medium-chain-length poly-(3-hydroxyalkanoates) (PHAMCL). The effect of these nitrogen sources on the cells growth, PHAMCL yield, monomer composition and molecular weight when this bacterium was cultivated on saponified palm kernel oil (SPKO) as the major carbon source was investigated. It was found that bacto-peptone gave significantly higher yield of residual biomass (PHA-free biomass) and PHAMCL as compared to ammonium salt, urea, yeast extract and beef extract. No significant difference in the monomer composition of the PHAMCL produced was observed with the different nitrogen sources. All the PHAMCL produced had high molecular weight, with the weight average (Mw) ranging from 90,000 to 127,000 and polydispersities (Mw/Mn) ranging from 1.7 to 1.9

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

High-rate fermentative hydrogen production from palm oil mill effluent in an up-flow anaerobic sludge blanket-fixed film reactor

The major problem associated with UASB reactors for biotransformation of organic matter to hydrogen is the long start-up period (2–4 months) required for the growth of the microbial granules. In this study, an integration of granular sludge system and a fixed film reactor in a single reactor was applied to overcome this problem. An up-flow anaerobic sludge blanket-fixed film (UASB-FF) reactor was initially inoculated with heat pretreated seed sludge as inoculum and operated as closed-loop fed-batch for five days (HRT = 24 h; 38 °C; pH 5.5). The reactor was continuously fed with fresh pre-settled POME in order to shorten the start-up period. The organic loading was gradually increased from 4.7 to 51.8 g/L d. Granular sludge rapidly developed within 22 days. Specific hydrogen production rate was 0.514 L H2/g VSS d at the end of the start-up period. Speedy development of bio-granules was attributed to biomass recirculation and the establishment of a fixed film at the upper section of the UASB-FF reactor that resulted in improved interactions among the bacterial consortium

Ultrasound degradation of xanthan polymer in aqueous solution: Its scission mechanism and the effect of NaCl incorporation

Degradation of xanthan polymer in aqueous solution by ultrasonic irradiation was investigated. The effects of selected variables i.e. sonication intensity, irradiation time, concentration of xanthan gum and molar concentration of NaCl in solution were studied. Combined approach of full factorial design and conventional one-factor-at-a-time was applied to obtain optimum degradation at sonication power intensity of 11.5 W cm−2, irradiation time 120 min and 0.1 g L−1 xanthan in a salt-free solution. Molecular weight reduction of xanthan gum under sonication was described by an exponential decay function with higher rate constant for polymer degradation in the salt free solution. The limiting molecular weight where fragments no longer undergo scission was determined from the function. The incorporation of NaCl in xanthan solution resulted in a lower limiting molecular weight. The ultrasound-mediated degradation of aqueous xanthan polymer chain agreed with a random scission model. Side chain of xanthan polymer is proposed to be the primary site of scission action

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