• Korean Journal of Weed Science
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• v.10 no.4
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• pp.328-337
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• 1990

The incividual and combined effects of the chloroacetanilide herbicide pretilachlor and of the safener fenclorim on the growth and selected physiological processes of rice (Oryza sativa L., var 'Lemont')were evaluated under greenhouse and laboratory conditions. Fenclorim applied at rates ranging from 50 to 300 g a.i./ha antagonized the injurious effects caused by 150 to 900 g a.i./ha of pretilachlor on 15-day old wet-sown rice grown under greenhouse conditions. When used rates of 150 g/ha or higher, fenclorim reversed completely the effects of all doses of pretilachlor on rice. When the two compounds were given simultaneously, fenclorim enhanced the uptake of $^{14}C$pretilachlor into rice leaf mesophyll protoplasts measured for 1 hr, indicating that competition for uptake at the protoplast level is not involved in the protective action of this safener. The safener-induced stimulation of pretilachlor uptake was particularly evident when fenclorim was used at concentrations of 10, 20 and $40{\mu}M$. Following 4 hr of incubation, individual treatments with pretilachlor inhibited the in vitro incorporation of radiolabeled precursors into proteins, DNA, and lipids of rice leaf protoplasts only when used at the high concentration of $100{\mu}M$M. Individual treatments with high concentrations (10 or $100{\mu}M$) of the safener fenclorim inhibited the incorporation of radiolabeled precursors into proteins and lipids of rice protoplasts, but had no DNA synthesis. The combined effects of pretilachlor and fenclorim on the incorporation of radiolabeled precursors into these macromolecules of isolated rice mesophyll protoplasts appeared to be additive or slightly synergistic rather than antagonistic. Fenclorim at $1{\mu}M$ antagonized the effects of pretilachlor on total lipids of rice leaf protoplasts. In addition, individual and combined treat-menu with pretilachlor and fenclorim influenced the incoroporation of$^{14}C$acetate into polar lipids, triglycerides and steryl esters of rice leaf protoplas causing a redistribution of carbon in these lipid fractions. However, these effects were not large enough to explain the herbicidal activity of pretilachlor or to account for the protective action of the safener fenclorim. Overall, the uesults of the present study idnicate that the safener fenclorim does not seem to protect rice against pretilachlor injury by antagonizing its effects on protein, DNA, or lipid syntheses.

• Microbiology and Biotechnology Letters
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• v.48 no.3
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• pp.344-357
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• 2020

Strain improvement and bioprocess development were undertaken to enhance hyaluronic acid(HA) production by Streptococcus zooepidemicus cells. Using a high-yielding mutant strain, statistical medium optimization was carried out in shake flask cultures, resulting in 52% increase in HA production (5.38 g/l) at the optimal medium composition relative to the parallel control cultures. For sufficient supply of dissolved oxygen (DO), which turned out to be crucial for enhanced production of HA, agitation system and speed were intensively investigated in 5 L bioreactor cultures. Increase in oxygen mass transfer coefficient (k_La) through increment of agitation speed (rpm) and 35% expansion of diameter of the newly-designed impellers showed significantly positive effects on HA production. By installing an expanded Rushton-turbine impeller for efficient break-down of sparged air, and an extended marine impeller above the Rushton-turbine impeller for efficient mixing of the air-born viscous fermentation broth, maximum amount of HA (9.79 g/l) was obtained at 450 rpm, 1.8 times higher level than that of the corresponding flask culture. Subsequently, the possibility of bioprocess scale-up to a 50 L bioreactor was investigated. Despite almost identical maximum HA production (9.11 vs 9.25 g/l), the average HA volumetric productivity (r_p) of the 50 L culture turned out only 74% compared to the corresponding 5 L culture during the exponential phase, possibly caused by shear damages imposed on the producing cells at the high stirring in the 50 L culture. The scale-up process could be successfully achieved if a scale-up criterion of constant oxygen mass transfer coefficient (k_La) is applied to the 50 L pilot-scale bioreactor system.