Atividade enzimática de isolados de rizóbia nativos da Amazônia Central crescendo em diferentes níveis de acidez

Abstract

As enzimas são proteínas vitais que catalisam reações bioquímicas com grande especificidade, sendo capazes de aumentar em até 10 14 vezes algumas reações, sem requerer condições extremas de pH, pressão e temperatura. Além de formarem a base do sistema metabólico dos organismos vivos, essas proteínas proporcionam enormes oportuni- RESUMOA importância das bactérias conhecidas como rizóbia no estabelecimento de leguminosas tem sido amplamente reconhecida. Porém, poucas são as informações referentes ao perfil enzimático dessas bactérias benéficas. O estudo objetivou investigar a influência do pH do meio sólido sobre a atividade enzimática de rizóbios nativos da Amazônia Central. Essa triagem constitui o primeiro passo no processo de seleção de microorganismos benéficos, como produtores de enzimas de aplicação biotecnológica. Nesse estudo, 64 isolados de rizóbia foram testados para a produção extracelular de amilase, lipase, pectinase e protease, em meio YMA modificado. Excetuando a atividade pectinolítica, todas as outras enzimas (amilase, lipase e protease) foram detectadas nos isolados investigados. Dois isolados (INPA R-975 e INPA R-926) exibiram atividades amilolíticas, lipolíticas e proteolíticas. Os índices enzimáticos amilolíticos e proteolíticos variaram significativamente entre os isolados e as condições de pH do meio de cultura. De maneira geral, as maiores atividades amilolíticas e proteolíticas foram exibidas pelos isolados INPA R-957, INPA R-915B e INPA R-991 em pH 6,5. O isolado INPA R-957 também se mostrou amilolítico e proteolítico nos pHs 5,0 e 8,0. Esse estudo mostrou que alguns rizóbios nativos da Amazônia representam fontes promissoras de amilase e protease de uso biotecnológico, sobretudo na tecnologia de alimentos. Palavras-chave: amilase, lipase, pectinase, protease, feijão caupi, soja. SUMMARYENzYMAtIC ACtIVItY OF NAtIVE CENtRAL AMAzONIAN RHIzOBIA StRAINS GROwN IN DIFFERENt LEVELS OF ACIDItY. the importance of rhizobia bacteria in the establishment of legume plants has been widely recognized. However, information is scarce regarding the enzymatic profiles of these beneficial bacteria. the objective of this study was to investigate the influence of pH of solid medium on enzymatic activity of native Central Amazonian rhizobia strains. this screening constitutes the first step in selecting beneficial microorganisms as enzyme producers. In this study, 64 strains of rhizobia were screened for extracellular amylolytic, lipolytic, pectinolytic and proteolytic activities on modified YMA. with the exception of pectinolytic activity, the other enzymatic activity groups (amylase, lipase and protease) were found in the strains investigated. two isolates (INPA R-975 and INPA R-926) exhibited amylolytic, lipolytic and proteolytic activities. the activity levels of the amylases and proteases varied significantly among strains of rhizobia and among pH conditions. In general, the highest amylase and protease activities were presented by isolates INPA R-957, INPA R-915B and INPA R-991 at pH 6.5. the INPA R-95...

Polyphasic characterization of forage legumes root nodule bacteria isolated from semiarid region in Brazil

“…All isolates were capable of growing in the medium supplemented with starch; however, only three isolates showed extracellular amylolytic activity (271-2, 291-4 and 391-12). According to Oliveira et al (2006a), the enzyme index (EI) is one of the most commonly used semiquantitative parameters to evaluate the ability of microorganisms to produce enzymes in solid media. The evaluation of enzyme-producing organisms directly correlates the diameter of the degradation halo with the degrading ability of microorganisms, and an EI ≥ 2.0 is recommended to consider a microorganism as a producer of enzymes in a solid medium.…”

“…Amylolytic activity was detected by inoculating 5 mL of iodine dye solution (0.2% v/v) on sevenday-old incubated plates. Positive activity was considered when a smooth yellow halo formed around the colony, contrasting with the dark blue medium, according to Oliveira et al (2006a).…”

Partial characterization of amylases of two indigenous Central Amazonian rhizobia strains

“…Nonetheless, studies on rhizobia amylases are still scarce. Recently, Oliveira et al (2006) reported the occurrence of extracellular amylases in rhizobia strains in solid and liquid media (Oliveira et al, 2007). The aim of this study was the production and characterization of extracellular amylases from two indigenous Central Amazonian rhizobia strains.…”

Polyphasic characterization of bacteria obtained from upland rice cultivated in Cerrado soil

“…12 Catalase activity was assayed according to Vermelho et al 9 For amylase and protease activities, we observed the formation of a translucid halo around the colonies, formed by the isolates inoculated on M9 solid medium containing 1% of starch and 2% of milk protein, respectively. 13 Cellulase activity was determined according to Cattelan et al 14 …”