Concentration of metabolites from <i>Phoma</i> sp. using microfiltration membrane for increasing bioherbicidal activity

Abstract

This study is focused on the concentration of fermented broth from <i>Phoma</i> sp. to increase its herbicidal activity. For this purpose, biomolecules produced by submerged fermentation using <i>Phoma</i> sp. were concentrated by hollow fiber microfiltration membranes. The membrane feed was separated into two streams (retentate and permeate) and the crude broth was concentrated to 10, 30, 50, 70 and 90% (relative to the initial volume). The retentate samples were submitted to bioassays (triplicate) for evaluating their phytotoxic effects on five young leaves of species of <i>Cucumis sativus</i> and also on pre-emergence of weeds as <i>Bidens pilosa</i> and <i>Amaranthus retroflexus</i>. The highest herbicidal activity was 80.7% obtained for a concentration of 30% in the retentate fraction. At this condition, the bioherbicide presented severe damage symptoms on the detached leaves of <i>Cucumis sativus</i> if compared to the crude fermented broth. In the pre-emergence of <i>B. pilosa</i> and <i>A. retroflexus</i>, 100% control was obtained for assays performed in a germination chamber. For greenhouse assays using the substrate, the control rate of <i>A. retroflexus</i> was dependent of concentration of bioherbicide. The promising results achieved in the research with membrane separation process allow us to propose and develop further studies for evaluating this technology in the concentration of other metabolites produced by fermentation which also have bioherbicidal activity.