Development of immobilized novel fungal consortium for the efficient remediation of cyanide-contaminated wastewaters

Free cyanide is a hazardous pollutant released from steel industries. Environmentally-safe remediation of cyanide-contaminated wastewater is required. In this work, Pseudomonas stutzeri (ASNBRI_B12), Trichoderma longibrachiatum (ASNBRI_F9), Trichoderma saturnisporum (ASNBRI_F10) and Trichoderma citrinoviride (ASNBRI_F14) were isolated from blast-furnace wastewater and activated-sludge by enrichment culture. Elevated microbial growth, rhodanese activity (82 %) and GSSG (128 %) were observed with 20 mg-CN L^-1. Cyanide degradation > 99 % on 3rd d as evaluated through ion chromatography, followed by first-order kinetics (r² = 0.94-0.99). Cyanide degradation in wastewater (20 mg-CN L^-1, pH 6.5) was studied in ASNBRI_F10 and ASNBRI_F14 which displayed increased biomass to 49.7 % and 21.6 % respectively. Maximum cyanide degradation of 99.9 % in 48 h was shown by an immobilized consortium of ASNBRI_F10 and ASNBRI_F14. FTIR analysis revealed that cyanide treatment alters functional groups on microbial cell walls. The novel consortium of T. saturnisporum-T. citrinoviride in the form of immobilized culture can be employed to treat cyanide-contaminated wastewater.

Improving mass transfer rates in microbial cell immobilization system for environmental applications: Synergistic interaction of cells on crude oil biodegradation

Among the various techniques used to clean up polluted environments, bioremediation is the most cost-effective and eco-friendly option. The diversity of microbial communities in a consortium can significantly affect the biodegradability of hazardous organic pollutants, particularly for in situ bioremediation processes. This is largely attributed to interactions between members of a consortium. In this study, the effect of internal diffusion limitations in substrate model biodegradation was firstly examined by immobilized bacterial cells at different particle sizes produced by the electrospray technique. According to the obtained results, for particles with large size, the effectiveness factors (η) were about 0.58-0.67, and the resistance to diffusive on the biodegradation rate was significant, while with decreasing the particle size, η increases and approaches about 1. After selection of suitable bead size, heavy crude oil biodegradation was investigated using a consortium consisting of three oil-degrading bacterial strains at different treatment systems. The removal rate in the suspended co-culture system stands at minimum value of 38% with all three strains which is an indicator of negative interactions among consortium members. Independent immobilization of microorganisms minimizes the competition and antagonistic interactions between strains and leads to more crude oil removal, so that, the biodegradation rate reached 60%.

Removal of gaseous tetrahydrofuran via a three-phase airlift bioreactor loaded with immobilized cells of GFP-tagged Pseudomonas oleovorans GDT4

Tetrahydrofuran (THF) is a common highly toxic cyclic aliphatic ether that frequently exists in waste gases. Removal of gaseous THF is a serious issue with important environmental ramifications. A novel three-phase airlift bioreactor (TPAB) loaded with immobilized cells was developed for efficient THF removal from gas streams. An effective THF-degrading transformant, Pseudomonas oleovorans GDT4, which contains the pTn-Mod-OTc-gfp plasmid and was tagged with a green fluorescent protein (GFP), was constructed. Continuous treatment of THF-containing waste gases was succeeded by the GFP-labelled cells immobilized with calcium alginate and activated carbon fiber in the TPAB for 60 days with >90% removal efficiency. The number of fluorescent cells in the beads reached 1.7 × 10¹¹ cells·g^-1 of bead on day 10, accounting for 83.3% of the total number of cells. The amount further increased to 3.0 × 10¹¹ cells·g^-1 of bead on day 40. However, it decreased to 2.5 × 10¹¹ cells·g^-1 of bead with a substantial increase in biomass in the liquid because of cell leakage and hydraulic shock. PCR-DGGE revealed that P. oleovorans was the dominant microorganism throughout the entire operation. The maximum elimination capacity was affected by empty bed residence time (EBRT). The capacity was only 25.9 g m^-3·h^-1 at EBRT of 80 s, whereas it reached 37.8 g m^-3·h^-1 at EBRT of 140 s. This work provides an alternative method for full-scale removal of gaseous THF and presents a useful tool for determining the biomass of a specific degrader in immobilized beads.

Efficient biosynthesis of γ-decalactone in ionic liquids by immobilized whole cells of Yarrowia lipolytica G3-3.21 on attapulgite

In this study, the biosynthesis of γ-decalactone (GDL) was successfully conducted in an ionic liquid (IL)-containing cosolvent system using immobilized cells of Yarrowia lipolytica G3-3.21 on attapulgite (ATG). We found the immobilized Y. lipolytica G3-3.21 cells in N-butyl-pyridinium tetrafluoroborate ([BPy]BF4) solution gave the highest activity of C16-Acyl-CoA oxidase and the maximum yield of GDL. The optimum immobilization conditions for the highest yield of GDL were 20 g/L of ATG, 1.5 % of CaCl2 and 2 % of sodium alginate (NaAlg). The optimal [BPy]BF4 content, buffer pH, reaction temperature, shaking speed, castor oil and glucose contents were 7.5 %, 26 °C, 150 rpm, 100 g/L and 10 %, respectively. Under the optimized conditions, the GDL yield was up to 8.05 g/L. After ten times of reuse, the GDL yield was 7.51 g/L, corresponding to 93.3 % of that obtained in the first batch, suggesting a good reusability and potential for industrial applications.