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GROWTH RATE OF MIXED RUMINAL BACTERIA AS A FUNCTION OF ENERGETIC SUBSTRATE CONCENTRATION IN BATH CULTURE CRESCIMENTO DE BACTÉRIAS RUMINAIS EM FUNÇÃO DA CONCENTRAÇÃO DE SUBSTRATO ENERGÉTICO EM MEIO DE CULTURA

Geicimara Guimarães, José Carlos Pereira, Rogério de Paula Lana and 2 more

Pesquisa Agropecuária Tropical · 2011

doi:10.5216/pat.v41i1.6672 (opens in a new tab)

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Abstract

The objective of this study was to evaluate levels of sucrose on microbial growth. Roll tubes were filled with 15.6 mL of buffer Chen, 1 mL of inocula (rumen fluid from fistulated steer at pasture), 1 mL of Trypticase or hydrolyzed casein (1 g L-1 as final concentration) and 2.4 mL of sucrose solutions (0.00 g L-1, 0.37 g L-1, 0.75 g L-1, 1.5 g L-1, 3.0 g L-1, 6.0 g L-1, 12.0 g L-1, and 24.0 g L-1), in triplicate. The pH was 5.56 at 0 h and 4.6 after 6 h, and 5.83 in 0 g L-1 and 4.18 above 1.5 g L-1 of sucrose. The optical density (OD-600 nm) and microbial protein (MP-595 nm) tended to stabilize after 12 h and 6 g L-1 of sucrose, with no interaction between them. The OD (6 h to 24 h mean values) was curvilinear (hyperbolic), as a function of sucrose concentration, followed the saturation kinetics of Michaelis-Menten, which is typical of enzymes systems, and was described by the following Lineweaver-Burk equation: 1/OD = 0.508*(1/sucrose) + 1.15, R&sup2; = 0.99. The theoretical maximum microbial growth (1/a = kmax) was 0.87 OD and the concentration of sucrose to reach half of kmax (b/a = Ks) was 0.44 g L-1 of sucrose. The microbial growth was affected by incubation time, substrate concentration, and culture medium acidification. KEY-WORDS: Lineweaver-Burk; Michaelis-Menten; pH; saturation kinetics; sucrose. O objetivo deste estudo foi avaliar os n&iacute;veis de sacarose no crescimento microbiano. Tubos de ensaio foram preenchidos com 16,5 mL de tamp&atilde;o (meio Chen), 1 mL de in&oacute;culo (l&iacute;quido de r&uacute;men de bovino em pasto), 1 mL de Tripticase ou case&iacute;na hidrolisada (1 g L-1 como concentra&ccedil;&atilde;o final) e 2,4 mL de solu&ccedil;&atilde;o de sacarose (0,00 g L-1; 0,37 g L-1; 0,75 g L-1; 1,5 g L-1; 3,0 g L-1; 6,0 g L-1; 12,0 g L-1; e 24,0 g L-1), em triplicata. O pH foi de 5,56 &agrave; 0 hora (h) e 4,6 &agrave;s 6 h, 5,83 em 0 g L-1 e 4,18 acima de 1,5 g L-1 de sacarose. A densidade &oacute;ptica (DO-600 nm) e de prote&iacute;na microbiana (MP-595 nm) tenderam a se estabilizar ap&oacute;s 12 h e 6 g L-1 de sacarose, sem ocorr&ecirc;ncia de intera&ccedil;&atilde;o. A DO (valores m&eacute;dios entre 6 h e 24 h) foi curvil&iacute;nea (hip&eacute;rbole), em fun&ccedil;&atilde;o da concentra&ccedil;&atilde;o de sacarose, seguiu o modelo de satura&ccedil;&atilde;o cin&eacute;tica de Michaelis-Menten, t&iacute;pico do sistema enzim&aacute;tico, e foi descrita pela seguinte equa&ccedil;&atilde;o de Lineweaver-Burk: 1/DO = 0.508*(1/sacarose) + 1.15, R&sup2; = 0,99. O crescimento microbiano m&aacute;ximo te&oacute;rico (1/a = kmax) foi de 0,87 DO e a concentra&ccedil;&atilde;o de sacarose para atingir a metade kmax (b/a = Ks) foi de 0,44 g L-1 de sacarose. O crescimento microbiano foi afetado pelo tempo de incuba&ccedil;&atilde;o, concentra&ccedil;&atilde;o de substrato e acidifica&ccedil;&atilde;o do meio de cultura. PALAVRAS-CHAVE: Cin&eacute;tica de satura&ccedil;&atilde;o; Lineweaver-Burk; Michaelis-Menten; pH; sacarose.

Abstract licence: CC BY

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