Pll Phang - Academia.edu (original) (raw)

Papers by Pll Phang

Applied Microbiology and …, 2002

Microbial alkaline proteases dominate the worldwide enzyme market, accounting for a two-thirds sh... more Microbial alkaline proteases dominate the worldwide enzyme market, accounting for a two-thirds share of the detergent industry. Although protease production is an inherent property of all organisms, only those microbes that produce a substantial amount of extracellular protease have been exploited commercially. Of these, strains of Bacillus sp. dominate the industrial sector. To develop an efficient enzyme-based process for the industry, prior knowledge of various fermentation parameters, purification strategies and properties of the biocatalyst is of utmost importance. Besides these, the method of measurement of proteolytic potential, the selection of the substrate and the assay protocol depends upon the ultimate industrial application. A large array of assay protocols are available in the literature; however, with the predominance of molecular approaches for the generation of better biocatalysts, the search for newer substrates and assay protocols that can be conducted at micro/nano-scale are becoming important. Fermentation of proteases is regulated by varying the C/N ratio and can be scaled-up using fed-batch, continuous or chemostat approaches by prolonging the stationary phase of the culture. The conventional purification strategy employed, involving e.g., concentration, chromatographic steps, or aqueous two-phase systems, depends on the properties of the protease in question. Alkaline proteases useful for detergent applications are mostly active in the pH range 8-12 and at temperatures between 50 and 70C, with a few exceptions of extreme pH optima up to pH 13 and activity at temperatures up to 80-90C. Alkaline proteases mostly have their isoelectric points near to their pH optimum in the range of 8-11. Several industrially important proteases have been subjected to crystallization to extensively study their molecular homology and threedimensional structures.

Circuits and Systems, 2005. ISCAS …, 2005

This paper presents a low-jitter VCO with on-chip supply regulation. Implemented in a digital 0.1... more This paper presents a low-jitter VCO with on-chip supply regulation. Implemented in a digital 0.18μm CMOS process, the design uses only the nominal 1.8V supply. The VCO has a tuning range from 72 MHz to 143 MHz and dissipates 11mW. At 140MHz, the VCO has an measured rms cycle jitter of 7.3ps with no supply noise. The benefits of on-chip regulation are demonstrated by superimposing a 200mVpp, 70MHz sine wave on top of the 1.8V power-supply. Without regulation, the jitter increases to 123 ps; with regulation, however, the measured rms cycle jitter is only 9.4ps.

Applied Microbiology and …, 2002

Microbial alkaline proteases dominate the worldwide enzyme market, accounting for a two-thirds sh... more Microbial alkaline proteases dominate the worldwide enzyme market, accounting for a two-thirds share of the detergent industry. Although protease production is an inherent property of all organisms, only those microbes that produce a substantial amount of extracellular protease have been exploited commercially. Of these, strains of Bacillus sp. dominate the industrial sector. To develop an efficient enzyme-based process for the industry, prior knowledge of various fermentation parameters, purification strategies and properties of the biocatalyst is of utmost importance. Besides these, the method of measurement of proteolytic potential, the selection of the substrate and the assay protocol depends upon the ultimate industrial application. A large array of assay protocols are available in the literature; however, with the predominance of molecular approaches for the generation of better biocatalysts, the search for newer substrates and assay protocols that can be conducted at micro/nano-scale are becoming important. Fermentation of proteases is regulated by varying the C/N ratio and can be scaled-up using fed-batch, continuous or chemostat approaches by prolonging the stationary phase of the culture. The conventional purification strategy employed, involving e.g., concentration, chromatographic steps, or aqueous two-phase systems, depends on the properties of the protease in question. Alkaline proteases useful for detergent applications are mostly active in the pH range 8-12 and at temperatures between 50 and 70C, with a few exceptions of extreme pH optima up to pH 13 and activity at temperatures up to 80-90C. Alkaline proteases mostly have their isoelectric points near to their pH optimum in the range of 8-11. Several industrially important proteases have been subjected to crystallization to extensively study their molecular homology and threedimensional structures.

Circuits and Systems, 2005. ISCAS …, 2005

This paper presents a low-jitter VCO with on-chip supply regulation. Implemented in a digital 0.1... more This paper presents a low-jitter VCO with on-chip supply regulation. Implemented in a digital 0.18μm CMOS process, the design uses only the nominal 1.8V supply. The VCO has a tuning range from 72 MHz to 143 MHz and dissipates 11mW. At 140MHz, the VCO has an measured rms cycle jitter of 7.3ps with no supply noise. The benefits of on-chip regulation are demonstrated by superimposing a 200mVpp, 70MHz sine wave on top of the 1.8V power-supply. Without regulation, the jitter increases to 123 ps; with regulation, however, the measured rms cycle jitter is only 9.4ps.