Optimization of laccase enzyme extraction from spent mushroom waste of Pleurotus florida through ANN-PSO modeling: An ecofriendly and economical approach

The application of laccase-rich extract of spent mushroom substrates for removing lignin from jute fabric waste: a dual management approach

Spent mushroom substrate (SMS) represents a growing waste from the mushroom cultivation sector due to increased popularity worldwide. SMS is rich in lignocellulolytic enzymes, allowing it to be recycled. Further, these enzymes can be applied to the sustainable use of natural fibers like jute, which need lengthy and expensive chemical processing methods. The study explored the dual sustainable management of two waste materials, SMS and jute fabric. SMS was examined as a source of lignin-degrading enzyme laccase to delignify jute and allow it to be processed sustainably. Response surface methodology (RSM) was applied to simultaneously optimize the extraction of laccase from various mushroom species SMS. Temperature, time of extraction, and pH were the independent variables evaluated in RSM. The most active enzyme was laccase from Pleurotus ostreatus SMS (P-SMS). RMS-based optimization of extraction enabled 1.47-fold increase in laccase activity. P-SMS laccase was partially purified, and its activity's optimal conditions (pH and temperature) were assessed. Jute fabric was treated with the extracted laccase under mild conditions (40˚C and pH 4.5), enabling the removal of 61.1% of the lignin, providing a softer and lighter appearance with an improvement in the wetting time confirmed by ATR-FTIR and polarized light microscopy. This work demonstrated the applicability of SMS-derived laccase extraction, using mild conditions to delignify jute fabric waste in an environmentally friendly way, thus creating a sustainable chain of waste processing steps.

Active site-inspired multicopper laccase-like nanozymes for detection of phenolic and catecholamine compounds

Phenolic compounds are typical organic pollutants which cause severe human health problems due to their teratogenesis, carcinogenesis, neurotoxicity, immunotoxicity and endocrine disruption. Natural laccase is a multicopper oxidase existing in bacteria, plants, and insects, which can accelerate the transformation of phenolic compounds to their less hazardous oxidized products under mild conditions without harmful byproducts. Despite eco-environmentally friendly property of laccase, it still faces constraints of widespread application attribute to its high cost, complex preparation, and vulnerability. Therefore, exploring laccase mimics with high catalytic activity attracts a lot of attention and endeavors. In this research, copper-based nanozymes were prepared with coordination of copper ions and imidazole for mimicking the active sites of natural laccase via solvothermal method. The obtained Cu-based (Cu-Im) nanozymes exhibited multiple redox valence states of Cu and laccase-mimicking coordination structures, which endow Cu-Im with high laccase-like activity. During the process of catalytic oxidation reactions, singlet oxygen and superoxide anions generated from oxygen. Encouraged by the catalytic property, Cu-Im was utilized in degradation and detection of phenolic and catecholamine compounds. The catalytic degradation of compounds by Cu-Im showed good conversion and substrate versatility, which can be used as a kind of potential materials for phenolic pollutant degradation and remediation. Simultaneously, colorimetric sensors of phenols and catecholamines based on Cu-Im in solution system and POCT pad platform were constructed which indicated wide linear range and low limit of detection for both detection strategies. The Cu-Im-based sensor was a promising method for sensitive, fast, convenient, and qualitative-quantitative colorimetric analysis of phenols and catecholamines. The outcomes of this research elucidate Cu-Im is a satisfactory substitute for natural laccase, which will have broad application prospects in laccase-related fields, such as environmental recovery, pollution monitoring, and diagnosis of neurological diseases etc.

Micropollutants (ciprofloxacin and norfloxacin) remediation from wastewater through laccase derived from spent mushroom waste: Fate, toxicity, and degradation

Fluoroquinolone antibiotics frequently found in environmental matrices (wastewater treatment plants, hospital wastewater, industrial wastewater and surface wastewater) causes potential threat to the environment. Enzymatic treatment for degradation of antibiotics from environmental matrices is a green and sustainable approach. Focusing on this, this study aimed to degrade two frequently found fluroquinolone emergent pollutants, ciprofloxacin and norfloxacin from wastewater. The trinuclear cluster of copper ions present in laccase has the ability to effectively remove organic micropollutants (OMPs). The uniqueness of this study is that it utilizes laccase enzyme extracted from spent mushroom waste (SMW) of P. florida for degradation of ciprofloxacin and norfloxacin and to achieve highest degradation efficiency various parameters were tweaked such as pH (3-6), temperature (30 °C and 50 °C), and ABTS (0.05, 0.6, and 1 mM) concentration. The results showed that the most effective degradation of ciprofloxacin (86.12-75.94%) and norfloxacin (83.27-65.94%) was achieved in 3 h at pH 4.5, temperature 30 °C, and 2,2'-azino-bis 3-ethylbenzothiazoline-6-sulfonic acid (ABTS), 0.05 mM concentration. Nevertheless, achieving degradation at 50 °C for both antibiotics, indicates thermostability nature of laccase (P. florida). Further, the fate of transformed products obtained from laccase mediated degradation was confirmed by liquid chromatography (LC-MS). Both the antibiotics undergo decarboxylation, depiperylyzation, dealkylation and defluorination as a result of laccase-mediated bond breakage. Anti-microbial activity of the biodegraded products was monitored by residual anti-bacterial toxicity test (E. coli and Staphylococcus aureus). The biodegraded products were found to be non-toxic and resulted in the growth of E. coli and Staphylococcus aureus, as determined by the agar-diffusion method. Moreover, the storage stability of laccase was determined for 28-day duration at varying pH (3-10) and temperature (4-50 °C). The maximum storage stability was obtained at pH 4.5 and temperature 30 °C. Therefore, utilizing SMW for the degradation of OMPs from wastewater not only benefits in degradation but also reuses SMW agro waste, shedding light on agro waste management. Thus, SMW is a one-pot solution for both OMPs biodegradation and circularity in the economy.

Enhanced production of mycelium biomass and exopolysaccharides of Pleurotus ostreatus by integrating response surface methodology and artificial neural network

This study aimed to enhance the production of mycelium biomass and exopolysaccharides (EPS) of Pleurotus ostreatus in submerged fermentation. Response Surface Methodology (RSM)sought to optimize culture conditions, whereas Artificial Neural Network (ANN)aimed to predict the mycelium biomass and EPS. After optimization of RSM model conditions, the maximum biomass (36.45 g/L) and EPS (6.72 g/L) were obtained at the optimum temperature of 22.9 °C, pH 5.6, and agitation of 138.9 rpm. Further, the Genetic Algorithm (GA) was employed to optimize the cultivation conditions in order to maximize the mycelium biomass and EPS production. The ANN model with an optimized network structure gave the coefficient of determination (R2) value of 0.99 and the least mean squared error of 1.9 for the validation set. In the end, a graphical user interface was developed to predict mycelium biomass and EPS production.