Pb(II) Bio-Removal, Viability, and Population Distribution of an Industrial Microbial Consortium: The Effect of Pb(II) and Nutrient Concentrations

Abstract

This study presents the effect of aqueous Pb(II) and nutrient concentrations on the Pb(II)-removal, biomass viability, active species identities, and population distribution of an industrial Pb(II) resistant microbial consortium. The studied consortium has previously shown to be highly effective at precipitating Pb(II) from solution. At all conditions tested (80 and 500 ppm Pb(II), and varying nutrients conditions) it was found that circa 50% of Pb(II) was removed within the first 3 h, with the absence of any visual changes, followed by a slower rate of Pb(II) removal accompanied by the formation of a dark precipitate. The Pb(II) removal was found to be independent of microbial growth, while growth was observed dependent on the concentration of Pb(II), nutrients, and nitrates in the system. SEM analysis indicated viable bacilli embedded in precipitate. These findings indicate that precipitation occurs on the surface of the biomass as opposed to an internal excretion mechanism. BLAST (Basic Local Alignment Search Tool) results indicated Klebsiella pneumoniae as the active species responsible for Pb(II) bioprecipitation for both the 80 and 500 ppm isolated colonies, while a diverse population distribution of organisms was observed for the streak plate analyses. A quicker microbial generation rate was observed than what was expected for Klebsiella pneumoniae, indicating that the overall consortial population contributed to the growth rates observed. This study provided insights into the factors affecting Pb(II) bio-removal and bioprecipitation by the investigated industrially obtained consortium, thereby providing invaluable knowledge required for industrial application.

Insight into the Metabolic Profiles of Pb(II) Removing Microorganisms

“…The following Pb(II), growth and nitrate results were adapted from the first part (33 h) of the results presented by Hörstmann et al [ 9 ]. These results are presented once more as the content forms part of the foundation for the current study, and the analyses conducted during this study were acquired from the same sample set [ 9 ].…”

“…Abiotic controls were included in a previous study by this team to verify any change being biological and not physicochemical [ 9 ]. The abiotic controls were examined over a period of 72 h, during which the Pb(II) concentration increased from 85 to 86.5 ppm, indicating a minute change in concentration (1.8%).…”

“…Various studies have proven effective Pb(II) removal from contaminated water or soil but not the recovery of Pb(II) in elemental form. Results previously presented by this team indicated that Pb(II) bioremoval was extremely effective under anaerobic conditions using an industrially obtained microbial consortium resulting in the formation of a dark precipitate with the presence of elemental Pb [ 7 , 8 , 9 ]. The consortium was characterized in a previous study conducted by Hörstmann et al, and the key Pb(II)-resistant and -removing microorganisms were found to be Klebsiella pneumoniae and Clostridium bifermentans [ 9 ].…”

“…Results previously presented by this team indicated that Pb(II) bioremoval was extremely effective under anaerobic conditions using an industrially obtained microbial consortium resulting in the formation of a dark precipitate with the presence of elemental Pb [ 7 , 8 , 9 ]. The consortium was characterized in a previous study conducted by Hörstmann et al, and the key Pb(II)-resistant and -removing microorganisms were found to be Klebsiella pneumoniae and Clostridium bifermentans [ 9 ]. A summary of a few studies conducted on Pb bioremediation is presented in Table 1 below, the summary also refers to the work conducted by this team [ 7 , 9 ].…”

“…The consortium was characterized in a previous study conducted by Hörstmann et al, and the key Pb(II)-resistant and -removing microorganisms were found to be Klebsiella pneumoniae and Clostridium bifermentans [ 9 ]. A summary of a few studies conducted on Pb bioremediation is presented in Table 1 below, the summary also refers to the work conducted by this team [ 7 , 9 ]. From these findings, it is apparent that the current study is of great interest as elemental Pb was positively identified in the precipitate as well as the ability of this consortium to remove Pb(II) concentrations of up to 2000 ppm with ease.…”