Abstract
Industrialization has come with environmental challenges. Industries like paper, printing, textile, leather and so on widely use chemical dyes whose waste treatment or degradability is difficult. Among various methods employed, the use of microbial enzymes is the most effective. The study aimed at producing laccase from identified yeast strains for potential industrial use in dye decolourization. Laccase produced by Kluyveromyces dobzhanskii DW1 and Pichia manshurica DW2 were purified and immobilized up to 65.2 and 73.1%, respectively. The crude, purified and immobilized forms of the enzymes were used to decolourize malachite green and methyl red dyes each at concentrations of 0.05 and 0.1 g/L. The highest percentage decolourization by K. dobzhanskii DW1 was 81.50% (immobilized) and 87.50% (purified), respectively for malachite green and methyl red dyes while P. manshurica DW2b (crude) had 84.40 and 76.89%, respectively. The Fourier transform infrared (FTIR) spectrum of the dyes was collected within a scanning range of 4000 to 400 cm-1. The spectrum of methyl red dye by the purified K. dobzhanskii DW1 laccase showed disappearance of some chemical groups (peak), while the crude P. manshurica DW2 laccase removed the main azo-group, alcohol/phenol and higher alkane (1487.17) groups. The spectrum of untreated malachite green also showed 25 peaks with one disulphide, 2 aliphatic halogens, 2 thio ethers, 3 sulphones, 4 imino groups among other chemical groups. The decolourization of the dye with the immobilized K. dobzhanskii DW1 laccase showed a spectrum of 17 peaks with the removal of the disulphide (420.5), one aliphatic halogen (C-I), thio ether, 2 sulphone, 4 imino and 2 higher alkanes, while the crude P. manshurica DW2 laccase removed the 2 aliphatic halogen, 4 imino, 1 amine, 2 alkane and 2 of the 3 alcohol/phenol chemical groups. The removal of the main components (azo chemical group) of the dyes proved their effectiveness in decolourisation and bioremediation of the textile wastes. Key words: Decolourisation, azo-dye, laccase, immobilized, FT-IR spectra.
Highlights
Large amounts of chemically different dyes generated by textile industries are discharged into the environment and have become a major concern in wastewater treatment (Grassi et al, 2011)
The removal of the main components of the dyes proved their effectiveness in decolourisation and bioremediation of the textile wastes
The laccase enzyme was immobilized on agar gel and percentage immobilization of enzyme of both K. dobzhanskii (65.2%) and P. manshurica (73.1%) showed that immobilization reduced the enzyme activity in comparison to free enzyme (100%)
Summary
Large amounts of chemically different dyes generated by textile industries are discharged into the environment and have become a major concern in wastewater treatment (Grassi et al, 2011). Discharge of wastewater containing synthetic dyes have carcinogenic health effects and have biodegradable difficulty due to their complex aromatic structure posing an environmentally important problem and this has persuaded environmental engineers to develop new techniques for treatment of such harmful compounds. Many methods are being used for dye removal; they include physical/chemical adsorption, oxidation, biological treatments (Akar et al, 2013), microbial biomass and enzyme treatments (Anjaneyulu et al, 2005). Among these methods, the use of microbial enzymes is most efficient for dye degradation/decolorization (Baldev et al, 2013; Pramanik and Chaudhuri, 2018). Many of the aforementioned methods are not successful in dye removals due to the following reasons: (i) the chemicals are only partially degraded; (ii) the azo-dyes are converted into the toxic metabolites, and (iii) the toxic chemicals are converted to secondary solid wastes with complex binding structure; which has to be either treated again or dumped (Behnajady et al, 2006)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
