RICARDO GENARI CARACTERÍSTICAS DE ... - SBI-Café - UFV

ABSTRACT
GENARI, Ricardo, M.S., Universidade Federal de Viçosa, December, 1999.
Characteristics of growth and pectinase production by Klebsiella oxytoca
isolated from coffee beans. Adviser: Daison Olzany Silva. Committee
Members: Jorge Luiz Cavalcante Coelho and Marisa Vieira de Queiroz.
The bacteria Klebsiella oxytoca, isolated from the interior of Coffea
arabica beans, obtained from the Universidade Federal de Viçosa plantation, in
Viçosa, MG, was grown in 2.8 L Erlenmeyer flasks containing 1,0 L of minimal
medium, pH 7,0, and Sigma citric pectin as sole carbon source, at a final
concentration of 0.3% (w/ v). The culture was incubated at 25ºC, without shaking,
for 24 hours and reached a population of 10 8 cells per milliliter in less than 20
hours. Generation time under these conditions corresponded to 60 minutes. The
growth rate at 37ºC, in this medium, differed little from the rates obtained at 25ºC
and 30ºC. K. oxytoca proved capable of growing in this same medium without
ammonium sulfate even under anaerobic conditions. The pectinolytic enzyme
produced was induced intracellular pectate lyase, which acts primarily on
unmethylated substrate. Optimal activity of this enzyme was obtained at a
temperature of 40ºC, pH 9.0, in the presence of magnesium ions. The pectate lyase
presented a Km of 4.51 mg/ mL and did not lose activity when stored at -18ºC for 9
months or when held at 40ºC for 1 hour and 40 minutes. The physico-chemical
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