Performances of Pichia kudriavzevii in decolorization, biodegradation, and detoxification of C.I. Basic Blue 41 under optimized cultural conditions

Environmental Impact of Textile Materials: Challenges in Fiber-Dye Chemistry and Implication of Microbial Biodegradation

Synthetic and natural fibers are widely used in the textile industry. Natural fibers include cellulose-based materials like cotton, and regenerated fibers like viscose as well as protein-based fibers such as silk and wool. Synthetic fibers, on the other hand, include PET and polyamides (like nylon). Due to significant differences in their chemistry, distinct dyeing processes are required, each generating specific waste. For example, cellulose fibers exhibit chemical inertness toward dyes, necessitating chemical auxiliaries that contribute to wastewater contamination, whereas synthetic fibers are a major source of non-biodegradable microplastic emissions. Addressing the environmental impact of fiber processing requires a deep molecular-level understanding to enable informed decision-making. This manuscript emphasizes potential solutions, particularly through the biodegradation of textile materials and related chemical waste, aligning with the United Nations Sustainable Development Goal 6, which promotes clean water and sanitation. For instance, cost-effective methods using enzymes or microbes can aid in processing the fibers and their associated dyeing solutions while also addressing textile wastewater, which contains high concentrations of unreacted dyes, salts, and other highly water-soluble pollutants. This paper covers different aspects of fiber chemistry, dyeing, degradation mechanisms, and the chemical waste produced by the textile industry, while highlighting microbial-based strategies for waste mitigation. The integration of microbes not only offers a solution for managing large volumes of textile waste but also paves the way for sustainable technologies.

Advances in the Application of the Non-Conventional Yeast Pichia kudriavzevii in Food and Biotechnology Industries

Pichia kudriavzevii is an emerging non-conventional yeast which has attracted increased attention for its application in food and biotechnology areas. It is widespread in various habitats and often occurs in the spontaneous fermentation process of traditional fermented foods and beverages. The contributions of P. kudriavzevii in degrading organic acid, releasing various hydrolase and flavor compounds, and displaying probiotic properties make it a promising starter culture in the food and feed industry. Moreover, its inherent characteristics, including high tolerance to extreme pH, high temperature, hyperosmotic stress and fermentation inhibitors, allow it the potential to address technical challenges in industrial applications. With the development of advanced genetic engineering tools and system biology techniques, P. kudriavzevii is becoming one of the most promising non-conventional yeasts. This paper systematically reviews the recent progress in the application of P. kudriavzevii to food fermentation, the feed industry, chemical biosynthesis, biocontrol and environmental engineering. In addition, safety issues and current challenges to its use are discussed.

Amine-amide functionalized graphene oxide sheets as bifunctional adsorbent for the removal of polar organic pollutants

Effective mitigation of polar organic impurities from industrial effluents is a global environmental challenge. Here, we describe the solvothermal synthesis of ammonia-functionalized graphene oxide (NH₃GO) sheets for adsorptive removal of diverse organic pollutants, such as cationic dye basic blue 41 (BB41), anionic dye methyl orange (MO), and ionic 4-nitrophenol (4-NP), in aqueous media. Structural analysis of NH₃GO suggest a potent role of surface acidic and basic binding sites in adsorption of targets through an interplay of dynamic experimental variables, e.g., contact time, pH, initial adsorbate concentration, adsorbent mass, and temperature. At an initial pollutant concentration of 20 mg/L, equilibrium adsorption capacities for BB41, MO, and 4-NP were estimated at 199.5, 64.0, and 54.1 mg/g, respectively, with corresponding partition coefficients of 4156, 79.4, and 14.3 L/g, respectively. Experimental data of all three organic pollutants are best fitted by the pseudo-second-order kinetic model. The adsorption isotherm of BB41 follows a multilayer adsorption pattern, while those of MO and 4-NP fit into a monolayer adsorption pattern. The endothermic and spontaneous nature of the adsorption processes has also been explored for the three targets on NH₃GO based on thermodynamic analysis. The prepared NH₃GO sheets appear to be a promising adsorbent for the removal of polar organic dyes and aromatics in the solution phase.

Mycoremediation of azo dyes using Cyberlindnera fabianii yeast strain: Application of designs of experiments for decolorization optimization

This study investigated the dye decolorization capacity of three yeast strains. Cyberlindnera fabianii was shortlisted for its high decolorization capacity and was further tested on various azo dyes. Based on the color of the biomass, and the UV-Vis analysis, Acid Red 14 was selected as a model dye, to examine the enzymatic biodegradation. The results showed significant increase in the intracellular and extracellular activities of laccase, tyrosinase, manganese peroxidase, and azoreductase. Phytotoxicity assessment indicated that the AR14 biodegradation by-products were not phytotoxic compared to the original dye molecules. Regarding the decolorization optimization, the screening of factors using the Plackett-Burman design showed that pH, dye concentration, and shaking speed had significant effects. These factors and their combined effect were evaluated using response surface methodology with the Box-Behnken model. The pH was the most significant factor, followed by dye concentration. The analysis of the contour plot and the 3D response surface diagram showed that the decolorization was inversely proportional to the increase in the initial dye concentration, but proportional to the initial pH and shaking speed. At optimal conditions (pH = 5.154, AR14 = 50 mg/L), C. fabianii could decolorize more than 97% of AR14 within 12 hr. PRACTITIONER POINTS: Cyberlindnera fabianii is a successful candidate for dye mycoremediation. Oxidase and reductase are the key enzymes involved in the biodegradation of azo dyes. By-products of Acid red 14 biodegradation are not phytoxic compared to the original dye. Design of experience tools enables to determine optimum conditions for efficient decolorization.

Toxic effects of Red-S3B dye on soil microbial activities, wheat yield, and their alleviation by pressmud application

This study examined the effect of Red-S3B textile dye on soil microbial activities, uptake of the dye by wheat plants and growth on the dye-contaminated soil. Moreover, pressmud (PM) application was investigated for its alleviative effect on wheat yield and dye uptake by plants. Preliminarily, soil was spiked with a wide concentration range (0, 100, 250, 500, 750 and 1000 mg kg^-1 soil) of Red-S3B dye and wheat was grown for 42-days. The dye did not suppress the activities of soil enzymes and growth of wheat seedlings at 100 mg kg^-1; however, beyond this level the dye had a linear negative effect on these attributes. With 1000 mg dye kg^-1 soil, wheat seedling biomass, viable microbial count, soil respiration, dehydrogenase, phosphatase, and urease activities decreased by 84%, 33%, 45%, 69%, 24%, and 11%, respectively as compared to uncontaminated soil. Moreover, phosphorus and potassium content in wheat shoot decreased, while the nitrogen content increased in Red-S3B contaminated soil. In the subsequent pot experiment, PM application (12.5 g kg^-1 soil) was assessed to alleviate the adverse effect of moderately toxic level of Red-S3B dye (500 mg kg^-1 soil) on wheat growth and yield. Root and straw biomass, and grain yield of wheat decreased by 13, 19 and 12%, respectively in Red-S3B contaminated soil as compared to uncontaminated soil. However, PM application to dye-contaminated soil retrieved the dye-induced reduction in root and straw biomass and grain yield to become statistically (p ≤ 0.05) at par with control plants. The color of Red-S3B was clearly visible in spikes depicting that plants absorbed Red-S3B but probably could not metabolize it. Amending the dye-contaminated soil with PM decreased Red-S3B content in awns from 78 to 37 mg kg^-1. Hence, it is concluded that Red-S3B textile dye is highly toxic to soil microbes and wheat plants at levels exceeding 100 mg kg^-1 soil. Soil application of PM alleviates the adverse effect of Red-S3B dye on wheat growth through reducing its uptake by plants.

Removal of Basic Brown 16 from Aqueous Solution Using Durian Shell Adsorbent, Optimisation and Techno-Economic Analysis

Azo dyes including C. I. Basic Brown 16 (BB16) are one of the coloured organic compounds that have adverse effects on human health and the environment. The current work aims to optimise the adsorption of C.I BB16 in aqueous solution using durian (Durio zibethinus murray) shell as a low-cost green adsorbent. Durian shell was characterised by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The adsorption process was optimised with response surface methodology (RSM) based on pH (4–8), time (30–240 min), durian shell dosage (0.1–1.0 g/L) and initial concentration of C.I BB16 (10–20 ppm). The removal efficiency was determined based on the reduction of chemical oxygen demand (COD) and the decolourisation of C.I BB16. The techno-economic analysis was described in the current work to know the economic feasibility of durian shells as an adsorbent. The SEM images showed that durian shell adsorbent has a smooth surface with no pores. FTIR spectra confirmed the presence of -C-O, =C–H, C=C, -C-O-C and O-H bonds in durian shell. Maximum decolourisation (77.6%) and COD removal (80.6%) for C.I BB16 was achieved with the interaction between pH, time and adsorbent dose and initial concentration of C.I BB16. The optimal operating factors for adsorption of C.I BB16 recorded at pH 8, time (30 min), durian shell dosage (1 g/L) and 15 mg /L of C.I BB16 concentrations were 77.61 vs. 74.26 (%) of C.I BB16 removal and 80.60 vs. 78.72 (%) of COD removal with an R2 coefficient of 0.94 at p < 0.05. The specific cost of durian shell coagulant production is USD 172.71 per ton which is lower than the market price of honeydew peels-activated carbon (HDP-AC) (USD 261.81) and the commercial market price of activated carbon which is USD 1000.00/tons. These findings indicated that the durian adsorbent provides alternative methods for treating hair dye wastewater. These findings indicated that durian shells have a high potential for the adsorption of C.I BB16 in aqueous solution.