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Axial dispersion model for upflow anaerobic sludge blanket reactors

Singhal A, Gomes J, Praveen VV, Ramachandran KB

Biotechnol Prog, 1998 Jul;14(4):645-8.
PMID: 9694688

Fluid flow in UASB reactors is usually described by multicompartment models consisting of separate ideally mixed zones, plug flow zones, and stagnant zones linked with bypassing flows and back-mixing flows. A closer look at UASB reactor behavior indicates that this complexity is unnecessary. Our study on the startup and steady-state operation of a UASB reactor shows that its fluid flow can be explained just as well with a simple axial dispersion model. The physical transitions, which occur in different zones of the UASB reactor as the microorganisms acclimate to the wastewater, are adequately described by the model. Further, the number of parameters, which is six in standard UASB reactor models, is reduced to four in the case of the axial dispersion model.
Amplifying the manganese scavenging potential of Streptococcus zooepidemicus to reactive oxygen species during production of hyaluronic acid

Mashitah MD, Masitah H, Ramachandran KB

Med J Malaysia, 2004 May;59 Suppl B:59-60.
PMID: 15468818

Streptococcus zooepidemicus (SZ) is an aerotolerant bacteria and its ability to survive under reactive oxidant challenge raises the question of the existence of a defense system. Thus growth, hyaluronic acid (HA) and hydrogen peroxide (H2O2) production by SZ in the presence of increasing concentration of Mn2+ were studied. The results suggested that the tested strain supported growth and HA production in cultures treated with 1 and 10 mM of Mn2+ regardless of H2O2 presence in the medium. This showed that SZ have acquired elaborate defense mechanisms to scavenge oxygen toxicity and thus protect cells from direct and indirect effect of this radical. In contrast, cells treated with 25 mM Mn2+ were sensitive, in which, the HA production was reduced considerably. Thus showing that the oxygen scavenger systems of the cells may be fully saturated at this concentration.
Studies on the kinetics of Isopropyl Palmitate synthesis in packed bed bioreactor using immobilized lipase

Kee CY, Hassan M, Ramachandran KB

Artif Cells Blood Substit Immobil Biotechnol, 1999 Sep-Nov;27(5-6):393-8.
PMID: 10595438

The objective of this research was to study the kinetics of synthesis of a commercially important ester - Isopropyl Palmitate (IPP) using immobilized lipase (Lipozyme IM). It was studied in a packed bed differential reactor. In order to establish the kinetics of the reaction, parameters such as linear velocity of the fluid through the reactor, particle size, substrate concentration, substrate molar ratio, temperature and water activity were studied. Operational and storage stability of the enzyme were also assessed. The reaction followed Michaelis-Menton kinetics as observed from the relationship of initial rate of the reaction as a function of substrate concentration. It was found that the optimum substrate concentration was 0.15M palmitic acid and isopropyl alcohol in 1:1 stoichiometric ratio. Inhibition by excess of isopropyl alcohol has been identified. The optimum temperature for the esterification reaction was found to be around 50 degrees C. The activation energy of this process was determined to be 43.67 kJ/mol. The optimum water content was 0.50%. The reaction rates were measured in the absence of any significant external diffusional limitations. Since internal diffusional limitations could not be eliminated, the kinetics observed is only apparent.
Rhodovulum sulfidophilum in the treatment and utilization of sardine processing wastewater

Azad SA, Vikineswary S, Chong VC, Ramachandran KB

Lett Appl Microbiol, 2004;38(1):13-8.
PMID: 14687209

Rhodovulum sulfidophilum was grown in settled undiluted and nonsterilized sardine processing wastewater (SPW). The aims were to evaluate the effects of inoculum size and media on the biomass production with simultaneous reduction of chemical oxygen demand (COD).
Growth and production of biomass of Rhodovulum sulfidophilum in sardine processing wastewater

Azad SA, Vikineswary S, Ramachandran KB, Chong VC

Lett Appl Microbiol, 2001 Oct;33(4):264-8.
PMID: 11559398

AIMS: Rhodovulum sulfidophilum was grown in sardine processing wastewater to assess growth characteristics for the production of bacterial biomass with simultaneous reduction of chemical oxygen demand.
METHODS AND RESULTS: Growth characteristics were compared in diluted and undiluted, settled and non-settled wastewater growing in anaerobic light and aerobic dark conditions; and also at different agitation speeds. The highest biomass (8.75 g l(-1)) and a reduction in chemical oxygen demand of 71% were obtained in unsettled, undiluted wastewater after 120 h culture with 15% inoculum. In settled wastewater, highest biomass (7.64 g l(-1)) and a COD reduction of 77% was also obtained after 120 h. Total biomass was higher (4.34 g l(-1)) after 120 h culture in anaerobic light compared to (3.23 g l(-1)) in aerobic dark growth.
CONCLUSIONS, SIGNIFICANCE AND IMPACT OF THE STUDY: Better performance, mean of total biomass (6.97 g l(-1) after 96 h), total carotenoids (4.24 mg g(-1) dry cell from 24 h) and soluble protein (431 microg ml(-1) after 96 h) were obtained from aerobic dark culture at 300 rev min(-1). The COD reduction, however, was lower (69%) after 96 h culture. Thus, the benefits in the production of bacterial biomass in non-sterilized sardine processing wastewater with the reduction of chemical oxygen demand could be achieved.