Effect of fungal pellet morphology on enzyme activities involved in phthalate degradation

Application of Fungus Enzymes in Spent Mushroom Composts from Edible Mushroom Cultivation for Phthalate Removal

Spent mushroom composts (SMCs) are waste products of mushroom cultivation. The handling of large amounts of SMCs has become an important environmental issue. Phthalates are plasticizers which are widely distributed in the environment and urban wastewater, and cannot be effectively removed by conventional wastewater treatment methods. In this study, SMCs are tested for their ability to remove phthalates, including benzyl butyl phthalate (BBP), di-n-butyl phthalate (DBP), and diethyl phthalate (DEP). Batch experiments reveal that BBP, DBP, and DEP can be degraded by the SMC enzyme extracts of four edible mushrooms: Pleurotus eryngii, Pleurotus djamor, Pleurotus ostreatus, and Auricularia polytricha. Potential fungus enzymes associated with BBP, DBP, and DEP degradation in SMCs (i.e., esterases, oxygenases, and oxidases/dehydrogenases) are uncovered by metaproteomic analysis using mass spectrometry. Bioreactor experiments indicate that the direct application of SMCs can remove BBP, DBP, and DEP from wastewater, through adsorption and biodegradation. The results of this study extend the application of white-rot fungi without laccases (e.g., Auricularia sp.) for the removal of organic pollutants which are not degraded by laccases. The application of SMCs for phthalate removal can be developed into a mycoremediation-based green and sustainable technology.

Enhanced esterase activity during the degradation of dibutyl phthalate by Fusarium species in liquid fermentation

Dibutyl phthalate (DBP) is one of the most abundantly produced and used plasticizers and is incorporated into plastic to make it more flexible and malleable. DBP has been found to be an environmental contaminant and reported as an endocrine disruptor. Therefore, it is crucial to develop ecofriendly alternatives to eliminate phthalate pollution. In the present research, the growth of F. culmorum and F. oxysporum in the presence of DBP was studied in liquid fermentation. The esterase activity, specific growth rate, and growth and enzymatic yield parameters were determined in DBP-supplemented media (1,500 or 2,000 mg/L) and in control medium (lacking DBP). These results show that in general, for both Fusarium species, the highest esterase activities, specific growth rates, and yield parameters were observed in media supplemented with DBP. It was observed that 1,500 and 2,000 mg of DBP/L did not inhibit F. culmorum or F. oxysporum growth and that DBP induced esterase production in both fungi. These organisms have much to offer in the mitigation of environmental pollution caused by the endocrine disruptor DBP. This study reports, for the first time, esterase production during the degradation of high concentrations (i.e., 1,500 and 2,000 mg/L) of DBP by F. culmorum F. oxysporum.

Biotransformation of Phthalate Plasticizers and Bisphenol A by Marine-Derived, Freshwater, and Terrestrial Fungi

Phthalate esters (PEs, Phthalates) are environmentally ubiquitous as a result of their extensive use as plasticizers and additives in diverse consumer products. Considerable concern relates to their reported xenoestrogenicity and consequently, microbial-based attenuation of environmental PE concentrations is of interest to combat harmful downstream effects. Fungal PE catabolism has received less attention than that by bacteria, and particularly fungi dwelling within aquatic environments remain largely overlooked in this respect. We have compared the biocatalytic and biosorptive removal rates of di-n-butyl phthalate (DBP) and diethyl phthalate (DEP), chosen to represent two environmentally prominent PEs of differing structure and hydrophobicity, by marine-, freshwater-, and terrestrial-derived fungal strains. Bisphenol A, both an extensively used plastic additive and prominent environmental xenoestrogen, was included as a reference compound due to its well-documented fungal degradation. Partial pathways of DBP metabolization by the ecophysiologically diverse asco- and basidiomycete strains tested were proposed with the help of UPLC-QTOF-MS analysis. Species specific biochemical reaction steps contributing to DBP metabolism were also observed. The involved reactions include initial cytochrome P450-dependent monohydroxylations of DBP with subsequent further oxidation of related metabolites, de-esterification via either hydrolytic cleavage or cytochrome P450-dependent oxidative O-dealkylation, transesterification, and demethylation steps - finally yielding phthalic acid as a central intermediate in all pathways. Due to the involvement of ecophysiologically and phylogenetically diverse filamentous and yeast-like fungi native to marine, freshwater, and terrestrial habitats the results of this study outline an environmentally ubiquitous pathway for the biocatalytic breakdown of plastic additives. Beyond previous research into fungal PE metabolism which emphasizes hydrolytic de-esterification as the primary catabolic step, a prominent role of cytochrome P450 monooxygenase-catalyzed reactions is established.

Morphological Characteristic Regulation of Ligninolytic Enzyme Produced by Trametes polyzona

A newly isolated white rot fungal strain KU-RNW027 was identified as Trametes polyzona, based on an analysis of its morphological characteristics and phylogenetic data. Aeration and fungal morphology were important factors which drove strain KU-RNW027 to secrete two different ligninolytic enzymes as manganese peroxidase (MnP) and laccase. Highest activities of MnP and laccase were obtained in a continuous shaking culture at 8 and 47 times higher, respectively, than under static conditions. Strain KU-RNW027 existed as pellets and free form mycelial clumps in submerged cultivation with the pellet form producing more enzymes. Fungal biomass increased with increasing amounts of pellet inoculum while pellet diameter decreased. Strain KU-RNW027 formed terminal chlamydospore-like structures in cultures inoculated with 0.05 g/L as optimal pellet inoculum which resulted in highest enzyme production. Enzyme production efficiency of T. polyzona KU-RNW027 depended on fungal pellet morphology as size, porosity, and formation of chlamydospore-like structures.

Macro-morphological characterization and kinetics of Mortierella alpina colonies during batch cultivation

An effective method for research of macro-morphological characterization and its kinetics was developed by studying the macro-morphological characteristics of Mortierella alpina, an oleaginous zygomycete widely used to produce lipids rich in PUFA, in function of culture medium composition and to link morphological features of fungus with the level of lipid production. A number of distinct morphological forms including hollow pellets, fluffy pellets and freely dispersed mycelia were obtained by changing the fermentation factors. By fitting a Logistic curve, the maximum specific growth rate (μmax)was obtained, which determined the final mycelia morphology. μmax of 0.6584 in three kind of morphological forms is the more appropriate. According to the Luedeking-Piret equation fitting, α≠0 and β≠0, lipid production was partially associated with the hyphal growth, fluffy pellets which turn glucose into lipidwas more effective than the other two kinds of morphological forms.

The filamentous fungal pellet-relationship between morphology and productivity

Filamentous fungi are used for the production of a multitude of highly relevant biotechnological products like citric acid and penicillin. In submerged culture, fungi can either grow in dispersed form or as spherical pellets consisting of aggregated hyphal structures. Pellet morphology, process control and productivity are highly interlinked. On the one hand, process control in a bioreactor usually demands for compact and small pellets due to rheological issues. On the other hand, optimal productivity might be associated with less dense and larger morphology. Over the years, several publications have dealt with aforementioned relations within the confines of specific organisms and products. However, contributions which evaluate such interlinkages across several fungal species are scarce. For this purpose, we are looking into methods to manipulate fungal pellet morphology in relation to individual species and products. This review attempts to address (i) how variability of pellet morphology can be assessed and (ii) how morphology is linked to productivity. Firstly, the mechanism of pellet formation is outlined. Subsequently, the description and analysis of morphological variations are discussed to finally establish interlinkages between productivity, performance and morphology across different fungal species.

A novel biodegradation pathway of the endocrine-disruptor di(2-ethyl hexyl) phthalate by Pleurotus ostreatus based on quantum chemical investigation

Di(2-ethyl hexyl) phthalate (DEHP) is a plasticizer that interfere with endocrine systems in mammals. Growth parameters for Pleurotus ostreatus grown on media containing glucose and different concentrations of DEHP (0, 500 and 1000mg/L) were evaluated. The highest biomass production was observed in medium supplemented with 1000mg of DEHP/L. Half-life of DEHP biodegradation, biodegradation constant of DEHP, and percentage of removal efficiency (%E) were also determined. P. ostreatus degraded 100% of DEHP after 504h. %E was 99.3% and 98.4% for 500 and 1000mg of DEHP/L, respectively. Intermediate compounds of biodegraded DEHP were identified by GC-MS and a DEHP biodegradation pathway was proposed using quantum chemical investigation. DEHP might be metabolized through three pathways; a de-esterification pathway, an oxidation pathway and an oxidation-hydrolysis pathway, forming phthalic acid, acetic acid and butanediol, respectively. P. ostreatus degrades and uses (as carbon and energy source) high concentrations of DEHP.

Degradation of di(2-ethyl hexyl) phthalate by Fusarium culmorum: Kinetics, enzymatic activities and biodegradation pathway based on quantum chemical modelingpathway based on quantum chemical modeling

Di(2-ethylhexyl) phthalate (DEHP) is a plasticizer widely used in the manufacture of plastics, and it is an environmental contaminant. The specific growth rate (μ), maximum biomass (Xmax), biodegradation constant of DEHP (k), half-life (t1/2) of DEHP biodegradation and removal efficiency of DEHP, esterase and laccase specific activities, and enzymatic yield parameters were evaluated for Fusarium culmorum grown on media containing glucose and different concentrations of DEHP (0, 500 and 1000mg/L). The greatest μ and the largest Xmax occurred in media supplemented with 1000mg of DEHP/L. F. culmorum degraded 95% of the highest amount of DEHP tested (1000mg/L) within 60h of growth. The k and t1/2 were 0.024h(-1) and 28h, respectively, for both DEHP concentrations. The removal efficiency of DEHP was 99.8% and 99.9% for 1000 and 500mg/L, respectively. Much higher specific esterase activity than specific laccase activity was observed in all media tested. The compounds of biodegradation of DEHP were identified by GC-MS. A DEHP biodegradation pathway by F. culmorum was proposed on the basis of the intermolecular flow of electrons of the identified intermediate compounds using quantum chemical modeling. DEHP was fully metabolized by F. culmorum with butanediol as the final product. This fungus offers great potential in bioremediation of environments polluted with DEHP.

Production of mycelial biomass by the Amazonian edible mushroom Pleurotus albidus

Edible mushroom species are considered as an adequate source of food in a healthy diet due to high content of protein, fiber, vitamins, and a variety of minerals. The representatives of Pleurotus genus are characterized by distinct gastronomic, nutritional, and medicinal properties among the edible mushrooms commercialized worldwide. In the present study, the growth of mycelial biomass of Pleurotus albidus cultivated in submerged fermentation was evaluated. Saccharose, fructose, and maltose were the three main carbon sources for mycelial biomass formation with corresponding yields of 7.28 g L⁻¹, 7.07 g L⁻¹, and 6.99 g L⁻¹. Inorganic nitrogen sources did not stimulate growth and the optimal yield was significantly higher with yeast extract (7.98 g L⁻¹). The factorial design used to evaluate the influence of saccharose and yeast extract concentration, agitation speed, and initial pH indicated that all variables significantly influenced the production of biomass, especially the concentration of saccharose. The greater amount of saccharose resulted in the production of significantly more biomass. The highest mycelial biomass production (9.81 g L⁻¹) was reached in the medium formulated with 30.0 g L⁻¹ saccharose, 2.5 g L⁻¹ yeast extract, pH 7.0, and a speed of agitation at 180 rpm. Furthermore, P. albidus manifested different aspects of morphology and physiology under the growth conditions employed. Media composition affected mycelial biomass production indicating that the diversification of carbon sources promoted its improvement and can be used as food or supplement.

Evaluation of the efficiency of Trametes hirsuta for the removal of multiple pharmaceutical compounds under low concentrations relevant to the environment

An evaluation of the efficiency of the White-rot fungi (WRF) Trametes hirsuta to remove multi-classes pharmaceutical active compounds (17 PhACs) at low and environmentally realistic concentrations (20-500 ng L(-1)) was performed. The importance of biosorption over enzymatic activity on PhACs removal was also evaluated. Results highlight the importance to consider environmentally relevant PhACs concentrations while evaluating the removal capacities of WRF in wastewaters treatment processes, as PhACs concentration strongly influence both the enzymatic activity profile and the removal efficiency. Results also show that under tested experimental conditions, laccase was the only active extracellular lignin modifying enzyme and that biosorption and possibly intracellular enzymes also contribute to the removal of some PhACs.

Effects of hydroxypropyl-β-cyclodextrin on the growth and morphology of Absidia coerulea

Cyclodextrin has been found to be an attractive novel solubilizer due to its unique material properties. Absidia coerulea is widely used in steroid bioconversion. The effects of hydroxypropyl-β-cyclodextrin (HP-β-CD) on the growth, morphology, and steroid-converting activity of A. coerulea CICC 40302 were systematically studied. HP-β-CD affected A. coerulea growth, resulting in changes in its spore morphology and mycelial morphology. It induced an increase in the spore germination rate and a decrease in cell biomass at the stationary phase. Optical microscopy revealed that HP-β-CD altered the mycelial morphology and reduced the pellet compactness of A. coerulea. A convenient and feasible computing method was used to measure pellet compactness, and it demonstrated that the compactness degree of the pellet decreased as HP-β-CD increased, which could be attributed to the modification of the physical properties of the fermentation medium. Moreover, the changing of mycelial morphology influenced steroid-converting activity. The results showed that HP-β-CD had multiple concentration-dependent effects on A. coerulea cells. HP-β-CD in the proper concentration range holds great potential as a biocompatible solubilizer.

Improvement of polygalacturonase production at high temperature by mixed culture of Aspergillus niger and Saccharomyces cerevisiae

Catabolic repression in the synthesis of inducible enzymes by glucose, fructose, and intermediates of the glycolytic cycle has been observed in many microorganisms. In order to enhance the polygalacturonase (PG) production of Aspergillus niger GJ-2, Saccharomyces cerevisiae J-1 was inoculated to the medium at 12h of culture, which resulted in a significant improvement of PG production. It was also found that maximum PG activity of 512.7 U/ml was obtained at 37°C in the mixed culture, which was nearly twofold higher than that of the culture without the inoculation of S. cerevisiae J-1.

Optimization of fumaric acid production by Rhizopus delemar based on the morphology formation

The effects of temperature, agitation rate and medium composition, including concentrations of glucose, soybean peptone, and inorganic ions, on pellet formation and pellet diameter of Rhizopus delemar (Rhizopus oryzae) NRRL1526 during pre-culture were studied. Inorganic ions and soybean peptone had negative and positive effects on pellet formation, respectively. The initial glucose and soybean peptone concentrations directly affected pellet diameter. Within a certain range, pellet diameter decreased with increased initial substrate concentrations; however, above this range there was an opposite trend. Thus, optimal concentrations of substrate during pre-culture were beneficial for producing small pellets of R. delemar. Furthermore, dry cell mass and yield of fumaric acid tended to increase with decreased pellet diameter. Based on the pellet morphology optimization, the final fumaric acid concentration was improved by 46.13% when fermented in a flask and 31.82% in stirred bioreactor tank fermentation.