Optimization and mechanisms for biodecoloration of a mixture of dyes by Trichosporon akiyoshidainum HP 2023

Evaluation of the sequential coupling of a bacterial treatment with a physicochemical process for the remediation of wastewater containing Cr and organic pollutants

A restoration strategy was developed for the treatment of two artificial liquid systems (Minimal Medium, MM, and Water Carbon Nitrogen, WCN) contaminated with Cr(VI), lindane (γ-HCH), phenanthrene (Phe), and reactive black 5 (RB5), through the use of an actinobacteria consortium, coupled with a physicochemical treatment using a column filled with nano-scale zero valent iron particles immobilized on dried Macrocystis pyrifera algae biomass. The Sequential Treatment A (ST_A: physicochemical followed by biological method) removed the three organic compounds with different effectiveness; however, it was very ineffective for Cr(VI) removal. The Sequential Treatment B (ST_B: biological followed by the physicochemical method) removed the four compounds with variable efficiencies. The removal of γ-HCH, Phe, and RB5 in both effluents did not present significant differences, regardless of the sequential treatment used. The highest removal of Cr(VI) and total Cr was observed in MM and WCN, respectively. Ecotoxicity tests (L. sativa) of the effluents treated with both methodological couplings demonstrated that the toxicity of WCN only decreased at the end of ST_A, while that of MM decreased at all stages of both sequential treatments. Therefore, MM would be more appropriate to perform both treatments.

Green synthesis of Quercus coccifera hydrochar in subcritical water medium and evaluation of its adsorption performance for BR18 dye

In this study, we investigated the production conditions of Quercus coccifera hydrochar, which is an inexpensive and easy available adsorbent, for the adsorption of Basic Red 18 (BR18) azo dye. The hydrochar was produced in the eco-friendly subcritical water medium (SWM). The effects of the pH (2-10), adsorbent size (45-106 μm), adsorbent dose (0.5-1.5 g/L), dye concentration (40-455 mg/L), and contact time (5-120 min) were studied via optimization experiments. The optimum conditions were pH 10, particle size of 45 μm, particle amount of 1.5 g/L, dye concentration of 455 mg/L, and 60 min. The removal efficiency increased sharply for the first 5 min; after that the removal efficiency reached a steady state at 60 min, with a maximum removal of 88.7%. The kinetic studies for the adsorption of BR18 dye in aqueous solution using hydrochar showed pseudo-second-order kinetics. The Langmuir and Freundlich isotherm models were used to explain the relationship between adsorbent and adsorbate, and Freundlich isotherm was the most suitable model because of its high regression coefficient (R²) value. The intraparticle diffusion model was used to determine the adsorption mechanism of BR18 onto Q. coccifera acorn hydrochar. Desorption studies were also carried out using different types of acid and different molarities.

Description of four Apiotrichum and two Cutaneotrichosporon species isolated from guano samples from bat-inhabited caves in Japan

Four new yeast species belonging to the genus Apiotrichum and two new yeast species belonging to Cutaneotrichosporon are described for strains isolated from guano samples from bat-inhabited caves in Japan. In 2005, we reported these isolates as Trichosporon species based on sequence analyses of the D1/D2 domain of large subunit (LSU) rRNA genes according to available basidiomycetous yeast classification criteria; however, to date, they have not been officially published as new species with descriptions. Their phylogenetic positions have been reanalysed based on comparison of internal transcribed spacer (ITS) region sequences (including the 5.8S rRNA gene) and the D1/D2 domain of the LSU rRNA gene with those of known species; we confirmed clear separation from previously described species. Physiological and biochemical properties of the isolates also suggest their distinctiveness. Therefore, we describe Apiotrichum akiyoshidainum (holotype JCM 12595^T), Apiotrichum chiropterorum (JCM 12594^T), Apiotrichum coprophilum (JCM 12596^T), Apiotrichum otae (JCM 12593^T), Cutaneotrichosporon cavernicola (JCM 12590^T) and Cutaneotrichosporon middelhovenii (JCM 12592^T) as new species. C. cavernicola showed particularly distinctive morphology including large inflated anomalous cells on the hyphae and germination from the cells, although clear clamp connections on the hyphae were not confirmed. Further study is needed to elucidate the morph of this species.

Process optimization for effective bio-decolourization of reactive orange 16 using chemometric methods

Azo group containing reactive dyes are most commonly used in textile and tannery industries due to its bright appearance and stable color. This study aims to investigate the decolourization of reactive orange 16 (RO16) dye by Pseudomonas aeruginosa 23N1 along with removal of chromate (Cr(VI)) and evaluation of optimal process condition. The regular two-level factorial design is used to screen out operational parameters and selects their levels for further optimization process through central composite design (CCD) based response surface methodology (RSM). The result revealed that glucose and peptone have a negative effect on the performance of dye decolourization. Bacteria exhibit high decolourization potential in yeast extract supplemented culture medium with no addition of external carbon sources. The percentages of decolourization obtained in model validated experiments are obtained as 95.0 ± 0.4% and 95.1 ± 0.5% for initial dye 50 mg/L and 150 mg/L, respectively, which exhibit satisfactory correlation with model predicted response. The simultaneous dye and Cr(VI) removal has been explored in this study. The decolourization of dye is only affected due to presence of high Cr(VI) concentration (>120 mg/L). Bacteria have shown satisfactorily decolourization for RO16 contaminated industrial wastewater. The strain 23N1 could be a good biological agent for decolourization of RO16 dye.

Genome-wide overview of Trichosporon akiyoshidainum HP-2023, new insights into its mechanism of dye discoloration

Trichosporon akiyoshidainum HP-2023 completely discolorised Reactive Black 5 (200 mg/l) in 24 h. Manganese peroxidase and phenoloxidase, but no laccase activities were detected throughout the incubation. Total aromatic amines in media with Reactive Black 5 decreased 83% after 24 h, supporting an oxidative mechanism of azo dye discoloration. To unravel the genetic basis of these activities, the genome of Trichosporon akiyoshidainum HP-2023 was sequenced, assembled and annotated de novo. T. akiyoshidainum HP-2023 genome comprises 30 MB with a G+C content of 60.75% and 9019 gene models. Thirty-three putative carbohydrate-active enzymes with auxiliary activities, probably involved in lignin degradation and dye discoloration, were identified in the annotated genome, including two laccases, four extracellular fungal heme-peroxidases, nineteen hydrogen peroxide-producing enzymes, and four benzoquinone oxidoreductases. This report will facilitate further studies of textile-dye discoloration with this and closely related strains and poses questions about the ligninolytic potential of Trichosporon akiyoshidainum HP-2023 and related species.