Bioremediation Using Bacillus subtilis and Saccharomyces cerevisiae to Reduce Chromium in Electroplating Liquid Waste

Abstract

<p>The electroplating industry produces liquid waste containing a small number of heavy metals but is toxic. Wastewater containing chromium (Cr) absorbed into the soil will affect soil fertility. Waste management is needed so that the abiotic and biotic environment is not poisoned by Cr. Bioremediation using bacterial and fungal microbes are applicable to reduce Cr levels in electroplating liquid waste. The purpose of this research was to investigate the reduction level of Cr in electroplating liquid waste through bioremediation using <em>Bacillus subtilis</em> and <em>Saccharomyces cerevisiae</em>. Laboratory experiments were conducted using variations in microbial concentrations (10^2.5cells ml^-1 and 10⁵ cells ml^-1), variations in microbial types (<em>Bacillus subtilis</em> bacteria, <em>Saccharomyces cerevisiae</em> fungi, and mixtures of both microbes), and variations in incubation time (6, 12, and 24 hours). The initial Cr concentration and the results of the bioremediation process were determined by measuring the absorbance and the Cr levels using Atomic Absorption Spectrophotometry (AAS). Based on experiments, the use of <em>Bacillus subtilis </em>10^2.5 cells ml^-1 with a 24-hour incubation time reach the highest percentage reduction in Cr (88.96%), followed by 12-hours incubation time (84.73%), and 6-hours incubation time (79.21%). Furthermore, the use of a microbial mixture of <em>Bacillus subtilis</em> and <em>Saccharomyces cerevisiae</em> 10^2.5 cells ml^-1 with 6-hours, 12-hours and 24-hours incubation time was able to reduce the levels of Cr respectively by 77.46%; 80.18% and 83.04%. Next, <em>Saccharomyces cerevisiae</em> 10⁵ cells ml^-1 with 6-hours, 12-hours, and 24-hours incubation time was able to reduce levels of Cr in a row by 50.17%; 52.35% and 55.63%. The results of this study indicate that the bioremediation process using the microbial <em>Bacillus subtilis</em> and <em>Saccharomyces cerevisiae</em> is proven to reduce the levels of Cr in the electroplating industry wastewater. The highest reduction results were achieved on the use of 24-hour incubation time and the use of <em>Bacillus subtilis</em> with a concentration of 10^2.5 cells ml^-1 at 88.96%.</p>