M. Suffian M. Annuar

Laccase production from oil palm industry solid waste: Statistical optimization of selected process parameters

Oil palm frond parenchyma tissue was used as a solid substrate for the production of laccase via solid‐state fermentation using the white rot fungus Pycnoporus sanguineus. With a rectangular aluminium tray as solid‐state fermentation bioreactor, process parameters such as bed height, moisture and supplemented nitrogen (as urea solution) levels were studied and optimized using a statistical design of experiment. The moisture level exerted a significant effect on the process. The interaction effect observed between bed height and supplemented nitrogen level suggested that uniform distribution of supplemented nitrogen into the substrate bed was important. The proposed regression model sufficiently predicted the process response over the experimental range tested. The optimum parameter combination for laccase production was a 3‐cm bed height, 72% w/w moisture and 0.21% w/v supplemented nitrogen. Laccase productivity remained constant when the tray size was increased from 1.4 to 3.4‐fold.

Phase inversion of medium-chain-length poly-3-hydroxyalkanoates (mcl-PHA)-incorporated nanoemulsion: effects of mcl-PHA molecular weight and amount on its mechanism

The study investigated the effects of molecular weight and amount of medium-chain-length poly-3-hydroxyalkanoates (mcl-PHA) on the formation of polymeric nanoparticle via phase inversion emulsification. Inversion from water-in-oil (W/O) to oil-in-water (O/W) emulsion through stepwise addition of water was affected by molecular weight and amount of incorporated mcl-PHA in the oil phase. The phase inversion mechanism depends upon molecular weight and amount of the incorporated mcl-PHA. It is hypothesized that at appropriate molecular weight and amount of mcl-PHA, the inversion occurs through the formation of bi-continuous/lamellar structure, in which the bulk composition of oil gradually decomposed into the desired nano-sized droplets. Otherwise, it will lead to an alternative phase inversion mechanism involving multiple emulsions resulting in larger nanoparticles with wider distribution.

Biotransformation of Momordica charantia fresh juice by Lactobacillus plantarum BET003 and its putative anti-diabetic potential

Lactobacillus plantarum BET003 isolated from Momordica charantia fruit was used to ferment its juice. Momordica charantia fresh juice was able to support good growth of the lactic acid bacterium. High growth rate and cell viability were obtained without further nutrient supplementation. In stirred tank reactor batch fermentation, agitation rate showed significant effect on specific growth rate of the bacterium in the fruit juice. After the fermentation, initially abundant momordicoside 23-O-β-Allopyranosyle-cucurbita-5,24-dien-7α,3β,22(R),23(S)-tetraol-3-O-β-allopyranoside was transformed into its corresponding aglycone in addition to the emergence of new metabolites. The fermented M. charantia juice consistently reduced glucose production by 27.2%, 14.5%, 17.1% and 19.2% at 15-minute intervals respectively, when compared against the negative control. This putative anti-diabetic activity can be attributed to the increase in availability and concentration of aglycones as well as other phenolic compounds resulting from degradation of glycosidic momordicoside. Biotransformation of M. charantia fruit juice via lactic acid bacterium fermentation reduced its bitterness, reduced its sugar content, produced aglycones and other metabolites as well as improved its inhibition of α-glucosidase activity compared with the fresh, non-fermented juice.

Triarylmethane Dye Decolorization by Pellets of Pycnoporus sanguineus: Statistical Optimization and Effects of Novel Impeller Geometry

ABSTRACT A study was carried out to optimize selected parameters for decolorization of a triarylmethane dye, such as crystal violet by white rot fungus, Pycnoporus sanguineus, pellets. The parameters studied were initial dye concentration (ppm), agitation speed (rpm), and process time (days) and were optimized using response surface methodology (RSM). It is shown that process time, agitation speed, and their interactions have significant effects on the decolorization process. Following the optimization, the decolorization study was extended to a stirred tank reactor (STR) process. Effects of different geometry of impellers on the decolorization process and power consumption were studied. Novel impeller geometries, such as 180° curved blade and 60° angled blade impellers, were used in the STR. The application of 180° curved blade impeller resulted in higher percentage of decolorization at a relatively less power consumption as compared with 60° angled blade impeller.

Dye decolorization by immobilized laccase: statistical optimization and effect of impeller geometry

Laccase enzyme from Trametes versicolor was immobilized using calcium-alginate entrapment method to decolorize triphenylmethane dye. Selected variables namely initial dye concentration (ppm), agitation speed (rpm) and process time (day) were optimized using response surface methodology (RSM) Box-Behnken design protocol. Under optimal conditions, good percentage of crystal violet decolorization was observed. Experiments were scaled up to a one litre (1 L) stirred tank reactor (STR) to examine the effects of impeller speed and geometry. In both the shake flask and stirred vessel study, lower initial dye concentration showed greater removal of dye. The dye removal achieved in the stirred tank ranged from 14 percent to 36 percent. A 6-blade mixed flow impeller (6MFD) showed better removal than a radial 6-curved blade (6CB) impeller, at the same agitation speeds, albeit with higher power demand. The effect of impeller speed depended on level of dye concentration and impeller type; speed was important at low concentration for the 6MFD while the exact opposite was true for the 6CB.

Functionalization of medium-chain-length poly(3-hydroxyalkanoates) as amphiphilic material by graft copolymerization with glycerol 1,3-diglycerolate diacrylate and its mechanism

ABSTRACT Glycerol 1,3-diglycerolate diacrylate (GDD) was graft copolymerized onto poly(3-hydroxyoctanoate-co-3-hydroxyhexanoate) P(3HO-co-3HHX) to render the latter more hydrophilic. Grafting of P(3HO-co-3HHX) backbone was performed using benzoyl peroxide as free radical initiator in homogenous acetone solution. The graft copolymer of P(3HO-co-3HHX)-g-GDD was characterized using spectroscopic and thermal methods. The presence of GDD monomer in the grafted P(3HO-co-3HHX) materials linked through covalent bond was indicated by spectroscopic analyses. Different parameters affecting the graft yield viz. monomer concentration, initiator concentration, temperature and reaction time were also investigated. Water uptake measurement showed that P(3HO-co-3HHX)-g-GDD copolymer became more hydrophilic as the GDD concentration in the copolymer increased. Introduction of hydroxyl groups via grafted GDD monomers improved the wettability and imparted amphiphilicity to the graft copolymer, thus potentially improving their facility for cellular interaction. Thermal stability of grafted copolymer reduced with increased grafting yield. The activation energy, Ea, for the graft copolymerization was calculated at ∼ 51 kJ mol−1. Mechanism of grafting reaction was also proposed.

A porous medium-chain-length poly(3-hydroxyalkanoates)/hydroxyapatite composite as scaffold for bone tissue engineering

Polyhydroxyalkanoates (PHA) are hydrophobic biopolymers with huge potential for biomedical applications due to their biocompatibility, excellent mechanical properties and biodegradability. A porous composite scaffold made of medium‐chain‐length poly(3‐hydroxyalkanoates) (mcl‐PHA) and hydroxyapatite (HA) was fabricated using particulate leaching technique and NaCl as a porogen. Different percentages of HA loading was investigated that would support the growth of osteoblast cells. Ultrasonic irradiation was applied to facilitate the dispersion of HA particles into the mcl‐PHA matrix. The different P(3HO‐co‐3HHX)/HA composites were investigated using field emission scanning electron microscopy (FESEM), X‐ray diffraction (XRD) and energy dispersive X‐ray analysis (EDXA). The scaffolds were found to be highly porous with interconnecting pore structures and the HA particles were homogeneously dispersed in the polymer matrix. The scaffolds biocompatibility and osteoconductivity were also assessed following the proliferation and differentiation of osteoblast cells on the scaffolds. From the results, it is clear that scaffolds made from P(3HO‐co‐3HHX)/HA composites are viable candidate materials for bone tissue engineering applications.

Adsorption and flotation of soluble crude protein by colloidal gas aphrons (CGA): effect of selected variables and process modeling

The adsorption and flotation of soluble crude protein from dairy products by colloidal gas aphrons (CGA) were studied. Selected process variables that were studied with respect to protein recovery include volume ratio between crude protein and CGA, stirring speed in the separation vessel, and contact time and surfactant concentration used to generate CGA. Cetyltrimethylammonium bromide (CTAB) in the buffered solution was used as the surfactant. It was found that only volume ratio between crude protein and CGA and surfactant concentration significantly influenced the protein recovery. The protein recovery achieved via its adsorption onto CGA surface and its subsequent flotation can be adequately modeled using Langmuir kinetics.