Enzymatic activity of native Central Amazonian rhizobia strains grown in different levels of acidity

Abstract

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-957 isolate also showed amylolytic and proteolytic activities at pH 5.0 and 8.0. This study revealed several Central Amazonian rhizobia strains as promising sources of amylase and protease for biotechnological applications, especially in food technology. © 2006 SBCTA.