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Articles by Thomas P. West
Total Records ( 6 ) for Thomas P. West
  Gang Xie and Thomas P. West
  Selected strains of the fungus Aspergillus niger were screened for their ability to produce citric acid on corn distillers` dried grains with solubles. It was determined that citric acid production by A. niger ATCC 11414 or ATCC 201122 after 240 h was higher on untreated grains than on autoclaved grains or acid-hydrolyzed grains. Methanol supplementation to the grains was only capable of stimulating citric acid production by A. niger strains ATCC 26550 and ATCC 11414. Biomass production by the selected strains after 240 h on the untreated and treated grains varied according to the strain being studied. The highest yield of citric acid was obtained for ATCC 11414 after it was supplemented with phosphate.
  Gang Xie and Thomas P. West
  Seven strains of the fungus Aspergillus niger were screened for their ability to produce citric acid on the ethanol dry milling coproduct thin stillage. Citric acid and biomass production by the fungal strains grown on the thin stillage were analyzed using an enzyme assay and a gravimetric method, respectively. Citric acid production by A. niger ATCC 9029, ATCC 9142, ATCC 10577, ATCC 12846, ATCC 26550 and ATCC 201122 was similar after 144 h of growth on thin stillage. These strains also exhibited high citric acid specific productivities and yields. Only the citric acid production, specific productivity and yield by A. niger ATCC 11414 were lower after growth on thin stillage. Biomass production by ATCC 9029 on thin stillage was the highest of the strains studied. For all strains, at least 88% of the reducing sugar concentration in the thin stillage was consumed after 144 h.
  Thomas P. West
  Three strains of the fungus Rhizopus oryzae were screened for their ability to produce fumaric acid on untreated or treated corn distillers` dried grains with solubles. The treatment of the grains included autoclaving alone or with low levels of sulfuric acid. After fungal growth, the grains were processed and fumaric acid production was assayed enzymatically while biomass production was determined gravimetrically. It was found that fumaric acid production by the three strains of R. oryzae after 240 h was higher on the autoclaved grains or acid-hydrolyzed grains compared to the untreated grains. Biomass production by R. oryzae ATCC 20344 after 240 h on the untreated and treated grains was higher than observed for R. oryzae ATCC 10260 and ATCC 52918. Fumaric acid productivity was higher for all three strains grown on the acid-hydrolyzed grains relative to their productivity on the untreated or autoclaved grains.
  Manuel F. Santiago and Thomas P. West
  The regulation of aspartate transcarbamoylase activity in cell extracts of Pseudomonas putida biovar B was examined. Under saturating substrate concentrations, ATP, UTP, GTP, ADP, UDP, UMP and pyrophosphate were highly inhibitory of the P. putida biovar B transcarbamoylase activity. By examining aspartate transcarbamoylase inhibition by ribonucleotides, it appeared that the P. putida biovar B strain could be differentiated from the P. putida biovar A strain which is consistent with previous taxonomic analyses that concluded biovar B strains should be reclassified.
  Thomas P. West
  Three distinct pathways to degrade pyrimidine bases in bacteria have been identified. The prevalent pathway of pyrimidine catabolism in species of Pseudomonas and Burkholderia is the reductive pathway. The reductive pathway consists of three enzymatic steps where uracil or thymine is degraded to β-alanine or β-aminoisobutyric acid, respectively. The enzymes dihydropyrimidine dehydrogenase, dihydropyrimidinase and β-ureidopropionase have been detected in a number of species of Pseudomonas and Burkholderia. The bacterial cell from these species were grown on pyrimidine bases as sole nitrogen sources and assayed for pyrimidine reductive catabolic enzyme activities using previously described assayed procedures. The three enzyme activities have been found to increase several fold depending upon the source of nitrogen and carbon used to grow the microorganisms. In species of Pseudomonas as well as Burkholderia cepacia, it was observed that pyrimidine bases induced the synthesis of the pyrimidine reductive pathway enzymes. The induction of the reductive pathway enzymes as well as other salvage enzymes in B. cepacia by 5-methylcytosine may indicate that pyrimidine catabolism in species of Pseudomonas and Burkholderia involves two additional enzymes. This possibility needs to be investigated to better understand whether pyrimidine catabolism is these microorganisms is more complex than originally thought. Overall, species of Pseudomonas and Burkholderia utilize the reductive pathway to provide a source of nitrogen from the catabolism of pyrimidine bases under nitrogen-limiting growth conditions.
  Thomas P. West
  The aim of this study was to determine if a curdlan overproducer Agrobacterium sp. mutant strain was able to produce higher levels of the polysaccharide than its parent strain from the grain processing coproduct condensed corn distillers solubles. The curdlan overproducer mutant was grown in a medium containing 400 g L-1 solubles for 120 h with curdlan and biomass levels being determined daily. The results with significant value were that curdlan could be produced at a higher level by the mutant strain on condensed corn distillers solubles as a source of carbon and nitrogen alone or supplemented with 3% corn syrup in less fermentation time than its parent strain. Other results with significant value was that the highest curdlan concentration was produced by the mutant strain (5.39 g L-1) or parent strain (4.97 g L-1) on condensed corn distillers solubles alone at 120 h. When the solubles were supplemented with corn syrup, the highest curdlan concentration was also produced by the mutant strain (12.34 g L-1) or parent strain (10.51 g L-1) at 120 h. Biomass production by ATCC 31749 (2.67 g L-1) was slightly higher than the mutant strain (2.50 g L-1) at 120 h of growth on condensed corn distillers solubles alone. When the solubles were supplemented with corn syrup, biomass production by the parent strain (4.25 g L-1) was much higher than the mutant strain (2.43 g L-1) at 120 h. The conclusion of this study with beneficial value is that the commercially valuable gum curdlan could be produced from a low value coproduct corn distillers solubles.
 
 
 
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