234 Black Wattle (Acacia mearnsii) Bark Tannin Most studies reporting inhibitory effects against microorganisms at high doses and stimulatory and positive health effects at low concentrations. Furthermore, previous studies showed that acacia tannin extracts induce changes in cell membrane and internal structures resulting in membrane rupture and organelle destruction of microorganisms.Vegetable tannin can inhibit different types of microorganisms and their distribution in the soil. Studies in forest soils demonstrate that additions of high concentrations of phenolic tannins compounds may affect the microbial population of the soil. In addition, soil organisms such as nematodes, annelids and arthropods may also be affected by the toxic effects of plant-based tannins. false false Traditionally, natural tannins have been used for tanning leather, but also there are a wide range of other industrial applications such as pharmaceutical use and water and sewage treatment, acting as flocculants 8,923