Statistical modeling of methylene blue degradation by yeast-bacteria consortium; optimization via agro-industrial waste, immobilization and application in real effluents

Abstract

The progress in industrialization everyday life has led to the continuous entry of several anthropogenic compounds, including dyes, into surrounding ecosystem causing arduous concerns for human health and biosphere. Therefore, microbial degradation of dyes is considered an eco-efficient and cost-competitive alternative to physicochemical approaches. These degradative biosystems mainly depend on the utilization of nutritive co-substrates such as yeast extract peptone in conjunction with glucose. Herein, a synergestic interaction between strains of mixed-culture consortium consisting of Rhodotorula sp., Raoultella planticola; and Staphylococcus xylosus was recruited in methylene blue (MB) degradation using agro-industrial waste as an economic and nutritive co-substrate. Via statistical means such as Plackett–Burman design and central composite design, the impact of significant nutritional parameters on MB degradation was screened and optimized. Predictive modeling denoted that complete degradation of MB was achieved within 72 h at MB (200 mg/L), NaNO3 (0.525 gm/L), molasses (385 μL/L), pH (7.5) and inoculum size (18%). Assessment of degradative enzymes revealed that intracellular NADH-reductase and DCIP-reductase were key enzymes controlling degradation process by 104.52 ± 1.75 and 274.04 ± 3.37 IU/min/mg protein after 72 h of incubation. In addition, azoreductase, tyrosinase, laccase, nitrate reductase, MnP and LiP also contributed significantly to MB degradation process. Physicochemical monitoring analysis, namely UV−Visible spectrophotometry and FTIR of MB before treatment and degradation byproducts indicated deterioration of azo bond and demethylation. Moreover, the non-toxic nature of degradation byproducts was confirmed by phytotoxicity and cytotoxicity assays. Chlorella vulgaris retained its photosynthetic capability (˃ 85%) as estimated from Chlorophyll-a/b contents compared to ˃ 30% of MB-solution. However, the viability of Wi-38 and Vero cells was estimated to be 90.67% and 99.67%, respectively, upon exposure to MB-metabolites. Furthermore, an eminent employment of consortium either freely-suspended or immobilized in plain distilled water and optimized slurry in a bioaugmentation process was implemented to treat MB in artificially-contaminated municipal wastewater and industrial effluent. The results showed a corporative interaction between the consortium examined and co-existing microbiota; reflecting its compatibility and adaptability with different microbial niches in different effluents with various physicochemical contents.

Pseudomonas alcaliphila NEWG-2 as biosorbent agent for methylene blue dye: optimization, equilibrium isotherms, and kinetic processes

“…Once the surface is saturated, MB diffuses into the material's interior, where adsorption continues, and subsequently lowers the adsorption rate 6 , 65 . Eltarahony et al 18 reported an equilibrium time of 2 h. Also, Ugraskan et al 66 mentioned that the ideal contact time was 90 min for the adsorption of MB onto porous boron carbide. While Ugraskan et al 66 reported that the optimum contact time of MB onto Judas tree ( Cercis siliquastrum ) seeds was determined to be 60 min, which agreed with our results.…”

“…Furthermore, agro-industrial waste was used as an economical and nutritive to recruit a consortium of Staphylococcus xylosus , Raoultella planticola , and Rhodotorula sp. in the biodegradation of MB 18 .…”

“…The bioremediation relies on the use of plants, microbes, and/or their enzymes. In this context, diverse microbial forms (living, dry biomass) under various environmental setups have been combined or sequentially documented 18 .…”

“…The Taguchi methods, on the other hand, are based on the philosophy of robust design and use a systematic design of experiments approach to study the effects of multiple factors simultaneously, considering the interactions between factors and identifying the optimal levels for the best response. The OFAT approach is limited and time-consuming, while the Taguchi methods provide a more comprehensive understanding of the process or system being studied 18 . The fractional factorial statistical Taguchi design is a robust and multi-optimization procedure.…”

Scaling-up strategies for controllable biosynthetic ZnO NPs using cell free-extract of endophytic Streptomyces albus: characterization, statistical optimization, and biomedical activities evaluation

“…The obtained pellet was re-suspended in 5 mL of sterile Milli Q water, incubated for 24 h at 28 °C, then centrifuged for 10 min at 13,000 rpm at 4 °C to get the extracellular extract 91 . Subsequently, the intracellular extract was obtained by sonicating the collected cells twice for 1.5 min each time with Milli Q at 600 kHz and 50% maximum power 92 . The extracellular and intracellular fractions were used as a reductant and a capping agent in the biosynthesis of ZnO NPs.…”