A variety of flocculants have been used to aggregate colloidal substances. However, recently, owing to the adverse effects and high costs of conventional flocculants, natural flocculants such as microbial flocculants are gaining attention. The aim of the study was to produce and characterize a bioflocculant from Pichia kudriavzevii MH545928.1 and apply it in wastewater treatment. A mixture of butanol and chloroform (5:2 v/v) was used to extract the bioflocculant. Phenol–sulphuric acid, Bradford and Carbazole assays were utilized for the identification of carbohydrates, proteins and uronic acid, respectively. Scanning electron microscopy (SEM) and elemental detector were employed to determine the surface morphology and elemental compositions. The removal efficiencies were 73%, 49% and 47% for BOD, COD and P, respectively. The bioflocculant (2.836 g/L) obtained showed the presence of carbohydrates (69%), protein (11%) and uronic acid (16%). The bioflocculant displayed a cumulus-like structure and the elemental composition of C (16.92%), N (1.03%), O (43:76%), Na (0.18%), Mg (0.40%), Al (0.80%), P (14.44%), S (1.48%), Cl (0.31%), K (0.34%) and Ca (20.35). It showed the removal efficiencies of 43% (COD), 64% (BOD), 73% (P) and 50% (N) in coal mine wastewater. This bioflocculant is potentially viable to be used in wastewater treatment.

Biolocculants are gaining attention in research due to their environmental friendliness and innocuousness to human in comparison to the conventional flocculants. The present study aimed to investigate the ability of fungi from Kombucha tea SCOBY to produce effective bioflocculant in bulk. A 16S rRNA gene sequence analysis was utilized to identify the isolate. The medium composition (carbon and nitrogen sources) and culture conditions (inoculum size, temperature, shaking speed, pH, and time) were optimized using one-factor-at-a-time method. The functional groups, morphology, and crystallinity of the bioflocculant were evaluated using Fourier transform infrared (FT-IR), scan electron microscope (SEM) and X-ray diffractometry (XRD). The fungus was found to be Pichia kudriavzevii MH545928.1. It produced a bioflocculant with flocculating activity of 99.1% under optimum conditions; 1% (v/v) inoculum size, glucose and peptone as nutrient sources, 35 °C, pH 7 and the shaking speed of 140 rpm for 60 h. A cumulus-like structure was revealed by SEM; FT-IR displayed the presence of hydroxyl, carboxyl, amine, and thiocynates. The XRD analysis demonstrated the bioflocculant to have big particles with diffraction peaks at 10° and 40° indicating its crystallinity. Based on the obtained results, P. kudriavzevii MH545928.1 has potential industrial applicability as a bioflocculant producer.

Over recent years, the ‘green’ chemistry approach to synthesizing nanoparticles has made significant developments. Because of their unique features, nanoparticles have received a lot of attention. The use of a bioflocculant to promote the environmentally friendly synthesis of copper nanoparticles is described in this paper. Copper nanoparticles were biosynthesized using bioflocculant which was produced from a yeast, Pichia kudriavzevii. The chemical reduction approach was used to synthesize copper nanoparticles (CuNPs) using a bioflocculant as a capping agent. Characterization of the as-synthesized copper nanoparticles was conducted using Fourier transform infrared (FT-IR) spectroscopy, UV-visible spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX). The FT-IR spectra revealed characteristic peaks at 3267, 2956, 1656, 1059, and 511 cm−1 for the bioflocculant, while for the bioflocculant passivated CuNPs, the characteristic peaks were at 3482 (-OH), 3261, 1640, 1059, 580, and 519 cm−1 (Cu-O). These peaks revealed that functional groups such as hydroxyls, amines, and copper oxide bonds were present. The UV-Vis analysis showed surface plasmon resonance (SPR) at an absorbance range of 500–600 nm, with peak maxima at 555 and 575 nm for the as-synthesized CuNPs. The XRD pattern revealed planes such as (200) and (220) at 2θ = 43 and 52°, and the particle size (30 nm) was determined by the Debye–Scherrer equation. The transmission electron microscopy analysis revealed a spherical-shaped particle with an average size of 20 nm. The EDX analysis of the as-synthesized CuNPs revealed the presence of the element Cu, which was not present in the EDX image of the bioflocculant used in the synthesis of the CuNPs; this indicated the success of biosynthesis.