Phenolic content and antioxidant activity of Tetraselmis tetrathele (West) Butcher 1959 cultured in annular photobioreactor.

Tetraselmis tetrathele (West) Butcher is an important microalgae due to its high antioxidant content and other bioactive compounds such as flavonoids and polyphenols. Therefore, it has potential as a suitable raw ingredient for various product developments in aquaculture, food and nutraceutical industries. The antioxidant activity of T. tetrathele (UPMC-A0007) was determined by culturing in f/2 and Conway media for 56 days in 120 l annular photobioreactors. The total phenolic (TPC) and antioxidant contents of T. tetrathele were determined six times during different phases of the culture period. The antioxidant activities of T. tetrathele's crude extract were determined by diphenylpicrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP) and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) assays. Two groups of cells based on size; small sized-cells (3.0-5.0?10-11g cell(-1)) and big sized-cells (5.5-8.0?10(-11) g cell(-1)) were observed in the f/2 media. Small sized-group showed 1.6 times higher total phenolic content (2.99?0.14 mg GAEg(-1)) than big sized-cells. These results suggest that T. tetrathele is a potential antioxidant source and effective antioxidant production can be achieved by controlling the cell size in their culturing process.

Improved integral backstepping control of variable speed motion systems with application to a laboratory helicopter.

This paper proposes an improved method of integral backstepping for real time control of a laboratory helicopter with variable speed rotors known as the Two-Rotor Aero-dynamic System (TRAS). The coupled system is decomposed into the horizontal subsystem (HS) and the vertical subsystem (VS) and traditional backstepping, augmented with direct integral action is designed for each subsystem. The transient response to both constant and time varying references is then simultaneously improved by modifying an already proposed method called dual boundary conditional integration. A switching technique is also employed to enhance the tracking response of the undamped HS for its bi-directional motor which exhibits jerking effects. Experimental results show that the proposed approach yields improved transient and tracking performance when compared to previously proposed methods exploiting conditional integration earlier proposed for improving the transient response of controlled nonlinear systems with integral action. The results also show the robustness of the proposed method in the presence of the coupling effects and additional external disturbance applied to the system in the form of a wind gust.

Scale-up synthesis of lipase-catalyzed palm esters in stirred-tank reactor.

Lipase-catalyzed production of palm esters by alcoholysis of palm oil with oleyl alcohol in n-hexane was performed in 2L stirred-tank reactor (STR). Investigation on the performance of reactor operation was carried out in batch mode STR with single impeller mounted on the centrally located shaft. Rushton turbine (RT) impellers provide the highest reaction yield (95.8%) at lower agitation speed as compared to AL-hydrofoil (AL-H) and 2-bladed elephant ear (EE) impellers. Homogenous enzyme particles suspension was obtained at 250 rpm by using RT impeller. At higher impeller speed, the shear effect on the enzyme particles caused by agitation has decreased the reaction performance. Palm esters reaction mixture in STR follows Newtons' law due to the linear relation between the shear stress (tau) and shear rate (dupsilon/dy). High stability of Lipozyme RM IM was observed as shown by its ability to be repeatedly used to give high percentage yield (79%) of palm esters even after 15 cycles of reaction. The process was successfully scale-up to 75 L STR (50 L working volume) based on a constant impeller tip speed approach, which gave the yield of 97.2% after 5h reaction time.

Lipase immobilized on poly(VP-co-HEMA) hydrogel for esterification reaction.

Lipase from Candida rugosa was immobilized by entrapment on poly(N-vinyl- 2-pyrrolidone-co-2-hydroxyethyl methacrylate) (poly[VP-co-HEMA]) hydrogel, and divinylbenzene was the crosslinking agent. The immobilized enzymes were used in the esterification reaction of oleic acid and butanol in hexane. The activities of the immobilized enzymes and the leaching ability of the enzyme from the support with respect to the different compositions of the hydrogels were investigated. The thermal, solvent, and storage stability of the immobilized lipases was also determined. Increasing the percentage of composition of VP from 0 to 90, which corresponds to the increase in the hydrophilicity of the hydrogels, increased the activity of the immobilized enzyme. Lipase immobilized on VP(%):HEMA(%) 90:10 exhibited the highest activity. Lipase immobilized on VP(%):HEMA(%) 50:50 showed the highest thermal, solvent, storage, and operational stability compared to lipase immobilized on other compositions of hydrogels as well as the native lipase.

Modified enzymes for reactions in organic solvents.

Recent studies on biocatalysis in water-organic solvent biphasic systems have shown that many enzymes retain their catalytic activities in the presence of high concentrations of organic solvents. However, not all enzymes are organic solvent tolerant, and most have limited and selective tolerance to particular organic solvents. Protein modification or protein tailoring is an approach to alter the characteristics of enzymes, including solubility in organic solvents. Particular amino acids may play pivotal roles in the catalytic ability of the protein. Attaching soluble modifiers to the protein molecule may alter its conformation and the overall polarity of the molecule. Enzymes, in particular lipases, have been chemically modified by attachment of aldehydes, polyethylene glycols, and imidoesters. These modifications alter the hydrophobicity and conformation of the enzymes, resulting in changes in the microenvironment of the enzymes. By these modifications, newly acquired properties such as enhancement of activity and stability and changes in specificity and solubility in organic solvents are obtained. Modified lipases were found to be more active and stable in organic solvents. The optimum water activity (a(w)) for reaction was also shifted by using modified enzymes. Changes in enantioselective behavior were also observed.

Immobilization of hydrophobic lipase derivatives on to organic polymer beads.

A simple and effective method of lipase immobilization is described. Lipase from Candida rugosa was first modified with several hydrophobic modifiers before being adsorbed on to organic polymer beads. The soluble hydrophobic lipase derivatives adsorbed more strongly on to the various polymers as compared with the native lipase. The optimal adsorption temperature of the native and modified lipases on all the polymers was 40 degrees C. The optimal pH of adsorption was between 6 and 7. Lipase immobilized in this manner produced high catalytic recoveries which are affected by the type of modifiers, degree of modification and type of supports used. Monomethoxypolyethylene glycol (1900) activated with p-nitrophenyl chloroformate was found to be the best modifier of the enzyme at 95% modification, for adsorption to the polymers. Increasing the degree of modification of the enzyme increased the activity which was immobilized. Generally, both native and hydrophobic lipase derivatives showed higher specific activities when immobilized on polar polymers compared with non-polar polymers.

Effect of compositions in nanostructured lipid carriers (NLC) on skin hydration and occlusion.

PURPOSE: To study the effects of varying lipid concentrations, lipid and oil ratio, and the addition of propylene glycol and lecithin on the long-term physical stability of nanostructured lipid nanocarriers (NLC), skin hydration, and transepidermal water loss. METHODS: The various NLC formulations (A1-A5) were prepared and their particle size, zeta potential, viscosity, and stability were analyzed. The formulations were applied on the forearms of the 20 female volunteers (one forearm of each volunteer was left untreated as a control). The subjects stayed for 30 minutes in a conditioned room with their forearms uncovered to let the skin adapt to the temperature (22°C ± 2°C) and humidity (50% ± 2%) of the room. Skin hydration and skin occlusion were recorded at day one (before treatment) and day seven (after treatment). Three measurements for skin hydration and skin occlusion were performed in each testing area. RESULTS: NLC formulations with the highest lipid concentration, highest solid lipid concentration, and additional propylene glycol (formulations A1, A2, and A5) showed higher physical stability than other formulations. The addition of propylene glycol into an NLC system helped to reduce the particle size of the NLC and enhanced its long-term physical stability. All the NLC formulations were found to significantly increase skin hydration compared to the untreated controls within 7 days. All NLC formulations exhibited occlusive properties as they reduced the transepidermal water loss within 7 days. This effect was more pronounced with the addition of propylene glycol or lecithin into an NLC formulation, whereby at least 60% reduction in transepidermal water loss was observed. CONCLUSION: NLCs with high lipid content, solid lipid content, phospholipid, and lecithin are a highly effective cosmetic delivery system for cosmetic topical applications that are designed to boost skin hydration.

Prevalence of eye diseases and visual impairment among the rural population - a case study of temerloh hospital.

OBJECTIVE: To determine the prevalence of eye diseases and visual impairment among new patients at the eye clinic of Hospital Sultan Haji Ahmad Shah, Temerloh, Pahang. METHOD: In this cross-sectional prospective study, 1081 new patients were examined over a period of six months. Age, gender, ethnicity, visual acuity and diagnosis were noted from the medical records. RESULTS: Out of 1081 examined, 607 (56.1%) were males, 783 (72.4%) were Malays. The mean age of patients was 45.2 years (ranging from one month to 91 years). Cataract (248, 22.9%) was the most common eye disease, followed by retinal diseases (124, 11.5%) and ocular trauma (106, 9.8%). Majority of the patients (48) suffering from ocular trauma had foreign body cornea. In 85 premature infants screened for retinopathy, 19 showed different stages of retinopathy of prematurity. Visual impairment was noted in 89 (8.2%) patients, severe visual impairment in 12 (1.1%) and blindness in 35 (3.2%); vision could not be determined in 85 premature infants (7.9%). Cataract was singled out as the cause of severe visual impairment in 11 out of 12 patients. CONCLUSION: Health education at primary health centres and availability of eye specialists in all the district hospitals will facilitate the rehabilitation of visually impaired and blind persons by providing early treatment for eye problems (specifically prescription for spectacles, medical treatment and cataract surgery with intraocular lens implantation).

Lipase-catalyzed esterification of palm-based 9,10-dihydroxystearic acid and 1-octanol in hexane--a kinetic study.

The esterification of palm-based 9,10-dihydroxystearic acid (DHSA) and 1-octanol in hexane as catalyzed by lipase from Rhizomucor meihei (Lipozyme IM) followed Michaelis-Menten kinetics. The esterification reaction follows a Ping-Pong, Bi-Bi mechanism. The maximum rate was estimated to be 1 micromol min(-1) mg(-1) catalyst in hexane at 50 degrees C, and the Michaelis-Menten constants for DHSA and 1-octanol were 1.3 M and 0.7 M, respectively.

Cloning and expression of a novel lipase gene from Bacillus sphaericus 205y.

A Bacillus sphaericus strain (205y) that produces an organic solvent-tolerant lipase was isolated in Port Dickson, Malaysia. The gene for the lipase was recovered from a genomic library and sequenced. Phylogenetic analysis was performed based on an alignment of thirteen microbial lipase sequences obtained from the NCBI database. The analysis suggested that the B. sphaericus lipase gene is a novel gene, as it is distinct from other lipase genes in Families I.4 and I.5 reported so far. Expression in Escherichia coli under the control of the lacZ promoter resulted in an eight-fold increase in enzyme activity after a 3-h induction with 1 mM IPTG. The crude enzyme thus obtained showed a slight (10%) enhancement in activity after a 30-min incubation in 25% (v/v) n-hexane at 37 degrees C, and retained 90% of its activity after a similar period in 25% (v/v) p-xylene.

A lipase from a newly isolated thermophilicRhizopus rhizopodiformis.

Two strains ofRhizopus rhizopodiformis that produced lipases in broth culture were isolated. Maximum lipase production (23 U/ml) was obtained after 72 h culture. Both the crude lipases were stable at 50°C for 30 min and at 45°C for 24 h. Maltose was the best carbon source and peptone the best nitrogen source for the production of lipases. Only glycerol and lecithin stimulated lipase production further.

Thermostable extracellular protease of Bacillus stearothermophilus: factors affecting its production.

A strain of protease-producing Bacillus stearothermophilus has been isolated. Glycerol was the best carbon source for production whereas yeast extract was the best nitrogen source. The bacterium could grow up to 70°C but optimum protease production was at 60°C. Best initial pH for protease production was 5. Alkaline pH inhibited production. The enzyme was stable at 60°C for 18 h and was inhibited by EDTA, PMSF and HgCl2.