3288 | wileyonlinelibrary.com/journal/jam J Appl Microbiol. 2022;133:3288–3295. © 2022 Society for Applied Microbiology. INTRODUCTION Water is one of the major sources for the survival of living organisms. In the era of emerging industrialization, the ecosystem is highly at threat by the release of untreated wastewater (Anita et al., 2020), especially, in textile dye- ing and other industrial sectors in which synthetic colours are exclusively employed. These industries consume more than 7 × 10 5 tonnes of different textile dyes each year, with wastewater containing 15%–20% of total textile dyes consumed, which has been found to have a significant impact on the environment (Wang et al., 2020b). The mal- achite green (MG), which belongs to the triphenylmeth- ane group, is the most common dye and is extensively used in textile dyeing industries (Balan et al., 2012; Roy et al., 2020). Laccase (EC1.10.3.2, benzenediol: oxygen oxidoreduc- tase) is a monomeric multi-copper enzyme that can reduce molecular oxygen to oxidize a variety of substrates includ- ing anilines, arylamines, ascorbic acid and phenols (Asadi et al., 2020; Debnath & Saha, 2020). Laccase, an environ- mentally beneficial and long-lasting catalyst, has been used Received: 21 February 2022 | Revised: 25 May 2022 | Accepted: 13 June 2022 DOI: 10.1111/jam.15670 ORIGINAL ARTICLE Laccase production from Bacillus aestuarii KSK using Borassus flabellifer empty fruit bunch waste as a substrate and assessing their malachite green dye degradation Kandasamy Selvam 1 | Fuad Ameen 2 | Mohammad Amirul Islam 3 | Chinnappan Sudhakar 1 | Thangaswamy Selvankumar 1 1 PG & Research Department of Biotechnology, Mahendra Arts and Science College (Autonomous), Namakkal, Tamil Nadu, India 2 Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, Saudi Arabia 3 Laboratory for Quantum Semiconductors and Photon-based BioNanotechnology, Department of Electrical and Computer Engineering, Faculty of Engineering, Université de Sherbrooke, Sherbrooke, Canada Correspondence Kandasamy Selvam, PG & Research Department of Biotechnology, Mahendra Arts and Science College (Autonomous), Kalippatti, Namakkal 637 501, Tamil Nadu, India. Email: ksk.selvam@gmail.com Funding information King Saud University, Grant/Award Number: RSP-2021/364 Abstract Aims: The lignocellulosic waste, Borassus flabellifer empty fruit bunch waste (BFEFBW), was employed to produce laccase using Bacillus aestuarii KSK under solid-state fermentation (SSF) conditions and to assess the efficiency of malachite green (MG) dye decolourization. Methods and Results: Abiotic factors such as pH (5.0–9.0), temperature (25–45°C) and incubation time (24–96 h) were optimized using Response surface methodology- Box-Behenan Design (RSM-BBD) to exploit the laccase production. The anticipated model revealed that the highest laccase activity of 437 U/ml shows after 60 h of in- cubation at 35°C at pH 7.0. The bacterial laccase was used to remove 89% of the MG dye in less time. Conclusion: The laccase from B. aestuarii KSK decolorizes the MG and thereby making it a suitable choice for wastewater treatment from industrial effluents. Significance and Impact of the Study: This study is the first report on the pro- duction of laccase from B. flabellifer empty fruit bunch waste as a substrate. Bacillus aestuarii KSK was isolated from the soil sample and used to produce laccase under SSF conditions. The bacterial laccase has the potential for industrial application in textile waste dye treatment. KEYWORDS Bacillus aestuarii KSK, laccase, malachite green dye decolourization, response surface methodology Downloaded from https://academic.oup.com/jambio/article/133/6/3288/6989133 by guest on 19 January 2023