Biodecolorization of Methylene Blue by Using <i>Bacillus subtilis</i> Immobilized into SA-PVA-Bentonite Matrix in Mineral Salt Medium and Non-nutritious Medium

Abstract

Industrial dye wastewater can potentially cause significant harm to organisms and the environment across the world. Methylene blue (MB) is a synthetic dye that can be found in wastewater. Immobilizing clay material and degradative bacteria into a carrier is the best way to remove MB. Therefore, this study aimed to immobilize Bacillus subtilis in sodium alginate (SA)-polyvinyl alcohol (PVA)-Bentonite for adsorption and degrading MB in nutritious mineral salt medium (MSM) and non-nutritious media. The result showed that SA-PVA-Bentonite-non-living B. subtilis beads (SPB-nBS) had the highest result in non-nutritious medium, approximately 88.89%. While in nutritious MSM, living B. subtilis addition into beads (SPB-BS) reached the highest MB removal, which was 94.31%. Nutritious MSM had a role as the sole carbon and energy for living B. subtilis. So, it could adsorb and degrade MB by its enzymatic system. The degradation products were predicted as C7H10N2O4S, C8H10N2O2 and C6H8N2O3S. Hence, this study indicated that a nutritious medium was the suitable medium for MB degradation. According to the SEM result, the bacteria spread and covered the beads. Furthermore, the adsorption kinetics and isotherms were also analyzed; SPB beads followed the pseudo-second order kinetic model and Langmuir isotherm.

Anionic dye removal by immobilized bacteria into alginate-polyvinyl alcohol-bentonite matrix

“…Nabilah et al [ 25 ] successfully removed methylene blue dye using a mixture of R. pickettii bacteria and Trichoderma viride fungi immobilized into SA-PVA-Bentonite. Rohmah et al [ 28 ] also showed that B. subtilis could decolorize and degrade methylene blue dye, while according to Upendar et al [ 31 ], the bacteria were immobilized into the suitable matrix. Generally, P. aeruginosa is one of the bacteria that is often used in study focused on the degradation of dye waste, indicating its potential to degrade methylene blue, methyl orange, reactive yellow, direct orange, etc [ [40] , [41] , [42] ].…”

“…The culture was transferred to another LB until the optical density (OD 600 ) touched a value of 1 and incubated at 37 °C to enter a stationary phase ( P. aeruginosa : 24 h, B. subtilis : 24 h, and R. pickettii : 44 h). Finally, 50 mL of each bacteria was taken, and centrifuged to obtain the biomass [ 28 , 29 ].…”

“…(1) , which was continued until the synthesized beads were damaged. Experiments on this treatment were also carried out in triplicate under sterile conditions [ 28 ].…”

“…Freeze-drying preparation was handled before characterization to remove the water content of beads. Subsequently, beads were characterized using Scanning Electron Microscopy (SEM) to determine their morphology and topology, indicating the surface and slicing appearance [ 28 ].…”

“…Consequently, MO requires a slightly longer time to be adsorbed in the adsorbent. Several studies have also added bacteria to the adsorption and degradation processes [ 23 , 28 ], including Bacillus subtilis to adsorb MB and obtained a maximum capacity of 37.01 mg/g [ 28 ]. The results showed that immobilized bacteria can still work for dye removal, as indicated by the SEM obtained [ 29 , 30 ].…”