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Articles by Rosfarizan Mohamad
Total Records ( 4 ) for Rosfarizan Mohamad
  Farliahati Mohd Rusli , Mohd Shamzi Mohamed , Rosfarizan Mohamad , Ni Nyoman Tri Puspaningsih and Arbakariya B. Ariff
  Problem statement: Interest in xylanase enzyme application has markedly increased in pulp and paper processing industries. The switch to xylanase-producing recombinant Escherichia coli DH5α pTP510 is seen here as an economic alternative towards higher productivity and easier downstream purification. Modeling of E. coli DH5α growth and enzyme secretion is thus desired for future optimization in fermentation process. Approach: Kinetics of intracellular xylanase fermentation by a recombinant E. coli DH5α was studied in shake flask culture. The effect of different medium formulations (complex, minimal and defined), initial pH (6.5, 7.0, 7.4 and 8.0) and agitation speeds (150, 200 and 250 rpm) on cell growth and xylanase production were evaluated. Mathematical models based on Logistic and Luedeking-Piret equations had been proposed to describe the microbial growth and xylanase production. Results: Highest xylanase production was obtained in defined medium. Based on medium formulation, the highest cell concentration (4.59 g L-1) and xylanase production (2, 122.5 U mL-1) was obtained when (NH4)2HPO4 was used as the main nitrogen source, with an adjustment of the initial pH to 7.4 and agitation speed of 200 rpm. The maximum specific growth rate (ยตmax), growth associated xylanase production coefficient (α) and non-growth associated xylanase production coefficient (β) was 0.41 h-1, 474.26 U mg cell-1and 0 U mg cell-1 h-1, respectively. Conclusion: Xylanase production was growth associated process and the enzyme secretion was greatly dependent on cell concentration and the specific growth rate of E. coli DH5α.
  Hii Siew Ling , Tau Chuan Ling , Rosfarizan Mohamad and Arbakariya B. Ariff
  Problem statement: Pullulanase is one of the important enzymes in starch industry. Search for the pullulanase with distinct features, possibly from easily grown bacterium, is of interest for industrial applications Approach: The extracellular pullulanase produced by Bacillus cereus HI.5 was purified by chromatographic method of DEAE-Sepharose, followed by Superdex gel filtration. The enzyme was characterized in terms of the optimal pH and temperature for activity as well as substrate specificity. Results: The enzyme showed optimal activity at 55°C and pH 6.0. The thermostability and the thermoactivity of the enzyme were increased considerably in the presence of Ca2+. In the present of 2 mM Ca2+, the enzyme had half-life duration of more than 2 h at 50°C. Almost all metal ions had a strong inhibitory effect, except Ca2+ and Mn2+. The Ca2+ had a very strong stimulating effect on the enzyme, increasing its activity by 170%. The enzyme was activated by 2-mercaptoethanol and dithiothreitol, where as N-bromosuccinimide and Schardinger dextrins were inhibitors, suggesting that tryptophan and thiol residues may be important for the activity. The apparent Km and Vmax value for pullulan was 1.1 mg mL-1 and 0.275 μmol min-1, respectively. A relative substrate specificity for hydrolysis of pullulan, amylopectin and soluble starch by this pullulanase was 100%, 28.5% and 20.4%, respectively. Conclusion: The enzyme was able to attack specifically the α-1,6 linkages in pullulan to generate maltotriose as the major end product, as well as the α-1,4 linkages in amylopectin and soluble starch leading to the formation of a mixture of maltose and glucose and therefore be classified as a type II pullulanase or an amylopullulanase.
  Mahdi Shahriarinour , Mohd Noor Abd Wahab , Arbakariya Ariff and Rosfarizan Mohamad
  Screening and isolation of cellulolytic fungi was done using compost of oil palm empty fruit bunch conducted at a local factory located in Sri Ulu Langat, Dengkil, Selangor, Malaysia. This research was aimed to isolate of cellulolytic fungi with over production of cellulase components. Ten isolated fungi had shown the ability to degrade cellulose base on decolorization of CMC selective agar using Grams iodine as color indicator and cellulase production in shake flask fermentation. Aspergillus (R4) was selected as over producer of cellulase enzyme among ten isolated fungi. The Aspergillus (R4) with highest clearing zone on CMC agar (50 mm) and cellulolytic activity (CMCase 3.05, FPase 0.61 and β-glucosidase 1.75 U mL-1) was identified as Aspergillus terrus. We identified Aspergillus terrues as highly cellulolytic in producing cellulase activity. Identification of over producers of cellulase enzymes can help industries exploits of this enzyme.
  Arezou Aghlara , Shuhaimi Mustafa , Yazid A. Manap and Rosfarizan Mohamad
  Headspace volatile flavor compounds of kefir were monitored using headspace solid phase microextraction (HS-SPME) method during fermentation of milk with kefir starter culture. Among all flavor compounds, forty volatile compounds were initially detected using gas chromatography coupled to time-of-flight mass spectrometer (GC-TOFMS). Consequently, eight volatile flavor compounds, namely ethanol, ethyl acetate, ethyl butyrate, 2-butanone, acetone, 3-hydroxy-2-butanone (acetoin), 2,3-butanedione (diacetyl) and acetaldehyde were considered as the representative of the alcohol, ketone, ester and aldehyde compounds in kefir. Moreover, in term of quantitative analysis, more than 97% of total flavor compounds composed of the proposed volatile flavor compounds. The results indicated that the concentration of 2-butanone released into headspace of kefir was found to be stable during fermentation. The release content of other volatile flavor compounds increased throughout the fermentation process. However, the headspace concentration of acetoin significantly (P < 0.05) decreased between pH 5.2 and 4.6.
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