Enhanced lignin peroxidase synthesis by Phanerochaete Chrysosporium in solid state bioprocessing of a lignocellulosic substrate

Matrine-producing endophytic fungus Galactomyces candidum TRP-7: screening, identification, and fermentation conditions optimization for Matrine production

Matrine (MA) is an alkaloid extracted from the root of genus Sophora with various pharmacological activities. Production of MA by endophytic fungi offers an alternative challenge to reduce the massive consumption to meet the increasing demand of MA. In the current study, the positive strains with MA producing ability were screened from endophytic fungal isolated from the root of Sophora tonkinensis Gagnep. Chromatographic analyses verified the identity of the produced MA. Among these fungi, Galactomyces candidum strain TRP-7 was the most valuable strain for MA production with the initial yield 8.26 mg L^-1. The MA production was efficiently maximized up to 17.57 mg L^-1 of fermentation broth, after optimization of eight process parameters using Plackett-Burman and Box-Behnken designs. The statistical optimization resulted in a 1.127 times increase in MA production as compared to the initial yield of TRP-7. This is the first report to isolate endophytic fungi with MA-producing activity from S. tonkinensis Gagnep., and to identify an endophytic fungus G. candidum TRP-7 as a new promising start strain for a higher MA yield.

Bioconversion of Some Agro-Residues into Organic Acids by Cellulolytic Rock-Phosphate-Solubilizing Aspergillus japonicus

Biological-based conversion of agricultural residues into bioactive compounds may be considered to be the basis for various vital industries. However, finding a suitable microorganism is a challenge in the bioconversion process. Therefore, this study was conducted to find local fungal isolates able to convert a combination of plant biomass residues into organic acids (OAs). Based on their cellulase and phytase activities and rock phosphate (RP) solubilization potential, an efficient 15 fungal isolates (named F1 to F15) were selected and identified by both morphological and molecular methods using the 18S rRNA sequencing technique. The best fungal isolate (F15) was identified as Aspergillus japonicus. After 4 weeks of incubation below solid-state fermentation (SSF) with a mix of sugarcane bagasse and faba bean straw (3:7), with 7.5% (v/w) fungal inoculum to the growth medium, the biodegradation process by the fungus reached its peak, i.e., maximum cellulolytic activity and RP solubilization ability. Under such fermentation conditions, seven organic acids were detected using HPLC, in the following order: ascorbic acid > oxalic acid > formic acid > malic acid > succinic acid > lactic acid > citric acid. Based on the results, Aspergillus japonicus (F15) could produce OAs and cellulose enzymes, and could be considered a new single-step bio-converter of sugarcane bagasse and faba bean straw residues into OAs. Furthermore, this fungus could be a new source of fungal cellulose, and could present a practical approach to reducing environmental contamination. Additional work is encouraged for more optimization of fermentation conditions.

Process performance improvement for the simultaneous production of ligninolytic enzymes in solid culture using agricultural wastes through the Taguchi method

Despite a large amount of published research on the production of ligninolytic enzymes, the latter are not yet being applied to combat environmental pollution. No cost-effective process has been developed to date. This study describes an improvement of the solid-state fermentation procedure for the production of ligninolytic enzymes via Phanerochaete chrysosporium ATX by applying the Taguchi method and using an agro-industrial waste as substrate. The production of lignin peroxidase (LiP), manganese peroxidase (MnP), and laccase (Lac) were simultaneously increased within a packed-bed column. The factors and levels studied were humidity (A: 60, 70, 80%), inoculum concentration (B: 7.5, 10.0, 12.5 × 10⁵ spores/mL), packed density (C: 0.14, 0.16, 0.18 g/mL), and time (D: 6, 8, 10 days). The results showed that humidity was the factor with a higher effect upon LiP and Lac's production, while time was for MnP. Humidity exerted the greatest influence on the global desirability of the process. Improved conditions (A, 60%; B, 1.0 × 10⁶ spores/mL; C, 0.17 g/mL; D, 8 days) were further validated: the results revealed an overall desirability increase of 237% over the unoptimized process. Process performance was likewise maintained at a higher scale (1:10). The results contribute to establishing a cost-effective bioprocess to produce ligninolytic enzymes by reducing the cost associated with raw materials and purification steps.

Fed-batch production of Thermothelomyces thermophilus lignin peroxidase using a recombinant Aspergillus nidulans strain in stirred-tank bioreactor

Enzymatic lignin depolymerization is considered a favorable approach to utilize lignin due to the higher selectivity and less energy requirement when compared to thermochemical lignin valorization. Lignin peroxidase (LiP) is one of the key enzymes involved in lignin degradation and possesses high redox potential to oxidize non-phenolic structures and phenolic compounds in lignin. However, the production of LiP is mainly from white-rot fungi at small scales. It is critical to discover new LiP from other microorganisms and produce LiP at large scales. This study aims to produce a novel LiP originally from Thermothelomyces thermophiles using a recombinant Aspergillus nidulans strain. The LiP production medium was optimized, and different fed-batch strategies for LiP production were investigated to improve LiP activity, yield, and productivity. Results demonstrated that LiP production was enhanced by using multi-pulse fed-batch fermentation. A maximum LiP activity of 1,645 mU/L with a protein concentration of 0.26 g/L was achieved.

Cultivation of Mushrooms and Their Lignocellulolytic Enzyme Production Through the Utilization of Agro-Industrial Waste

A large amount of agro-industrial waste is produced worldwide in various agricultural sectors and by different food industries. The disposal and burning of this waste have created major global environmental problems. Agro-industrial waste mainly consists of cellulose, hemicellulose and lignin, all of which are collectively defined as lignocellulosic materials. This waste can serve as a suitable substrate in the solid-state fermentation process involving mushrooms. Mushrooms degrade lignocellulosic substrates through lignocellulosic enzyme production and utilize the degraded products to produce their fruiting bodies. Therefore, mushroom cultivation can be considered a prominent biotechnological process for the reduction and valorization of agro-industrial waste. Such waste is generated as a result of the eco-friendly conversion of low-value by-products into new resources that can be used to produce value-added products. Here, we have produced a brief review of the current findings through an overview of recently published literature. This overview has focused on the use of agro-industrial waste as a growth substrate for mushroom cultivation and lignocellulolytic enzyme production.

Biological Pretreatment by Solid-State Fermentation of Oat Straw to Enhance Physical Quality of Pellets

Pelleting can increase the efficiency of handling and transportation of biomass. Pretreatment obtains lignin fragments by disrupting the lignocellulosic structure of biomass and ensures the high-quality compressed pellets. In this study, solid-state fermentation (SSF) is used as a biological method to improve the quality of pellets of oat straw. SSF of oat straw using Trametes versicolor 52J (TV52J) and Phanerochaete chrysosporium (PC) was conducted. Response surface methodology (RSM) was employed by using a four-factor, three-level Box–Behnken design with fermentation time (days), moisture content (%), particle size (mm), and fermentation temperature (°C) as independent parameters. Pellet density, dimensional stability, and tensile strength were the response variables. The optimization options of fermentation time (33.96 and 35 days), moisture content (70%), particle size (150 and 50 mm), and fermentation temperature (22°C) of oat straw pretreated with these two fungal strains were obtained. The microscopic structural changes of oat straw caused by biological pretreatment were investigated by scanning electron microscopy (SEM). Observation results of SEM showed that the connection between single fibers became relatively loose, and this was beneficial to improve the physical quality of the pellets.

Fibre degradation of wheat straw by Pleurotus erygnii under low moisture conditions during solid-state fermentation

The application of solid-state fermentation offers an alternative to conventional, submerged approaches for a variety of bioconversion processes, including animal feeds, biofuels and fungal bioproducts. Optimizing solid-state fermentation under low moisture conditions could significantly impact the proportion of dry biomass that could be processed and improve the commercial viability of this approach, because of reduced input costs and higher yields of final products. Pleurotus erygnii that appeared to show tolerance to low moisture conditions was grown on saturated and desaturated wheat straw. Pleurotus erygnii showed insignificant fibre degradation although showed significantly lower biomass decomposition on desaturated wheat straw. Fibre decomposition by the fungus on wheat straw containing wheat bran showed marginally higher decomposition when saturated although there was no difference in biomass decomposition. The levels of delignification achieved were similar under different saturation conditions. It would appear that the fungus effectively decomposed fibre under low moisture conditions often resulting in lower biomass losses. SIGNIFICANCE AND IMPACT OF THE STUDY: In this study, a white rot fungus, Pleurotus erygnii, effectively decomposed fibre under low moisture conditions when grown on wheat straw at similar levels under higher moisture conditions. However, the addition of wheat bran to wheat straw created a heterogeneous system that appeared to allow P. erygnii to thrive under much lower moisture conditions although lower levels of fibre decomposition was obtained. These factors could influence the preparation of solid-state fermentation.

Bio-bleaching of Remazol brilliant blue-19 by Stereum ostrea

Efficiency of white-rot fungi-Stereum ostrea (S. ostrea) as a test culture and Phanerochaete chrysosporium (P. chrysosporium) as a reference culture in colour removal from a textile dye, Remazol brilliant blue-19 (RBB-19) in medium was compared in this study. S. ostrea was more efficient than P. chrysosporium in decoloration process. Different parameters pH, temperature, sources of carbon and nitrogen, stationary and shaking conditions were optimized for bleaching of dye by the fungal cultures. Optimal growth conditions for decoloration of dye by both cultures were pH 5.0, temperature 35 °C, glucose and fructose as best carbon source at 1 % level, peptone and urea as best nitrogen source and shaking conditions (150 rpm). Culture broth free of colour (99 % of decoloration) was achieved with S. ostrea as against 70 % decoloration by P. chrysosporium on 6th day of incubation. Adsorption of dye to fungal biomass as reflected by colour coating on biomass and participation of lignolytic enzymes in colour removal appeared to be mechanisms involved in decoloration process. The ability of both fungal cultures in removal of colour in effluents with dyes collected from silk saree-weaving cottage unit was tested. S. ostrea was also found to be more effective in colour removal from effluent. S. ostrea appears to be a promising culture for application of bioremediation in decoloration of dyes.

Optimization of culture condition for enhanced decolorization and degradation of azo dye reactive violet 1 with concomitant production of ligninolytic enzymes by Ganoderma cupreum AG-1

The strain Ganoderma cupreum AG-1 (Genbank accession no. HQ328947) isolated from the decayed wood was evaluated for its ability to decolorize azo dye reactive violet 1 as well as for the production of ligninolytic enzymes. In the initial decolorization study, the strain was capable of decolorizing 19 different azo dyes. The strain was capable of decolorizing dye over a pH range of 4.5–6 at 30 °C. The optimum pH was found to be 4.5. Various other process parameters like additional carbon and nitrogen source and initial dye concentration were also optimized. The decolorization medium was supplemented with appropriate nitrogen source (yeast extract, 5 g l⁻¹) and carbon source (mannose, 2 g l⁻¹); the decolorization obtained was 98 %. The pattern of enzymes involved in the biodegradation was studied and laccase and MnP were found to be the major enzymes. High laccase activity shown by G. cupreum AG-1 and its ability to decolorize dyes are a good indication of its possible use in the treatment of textile effluents.

Degradation and mineralization of azo dye reactive blue 222 by sequential Photo-Fenton's oxidation followed by aerobic biological treatment using white rot fungi

A two stage sequential Photo-Fenton's oxidation followed by aerobic biological treatment using two white rot fungi P. ostreatus IBL-02 (PO) and P. chrysosporium IBL-03 (PC) was performed to check decolorization and to enhance mineralization of azo dye Reactive Blue 222 (RB222). In the first stage, selected dye was subjected to Photo-Fenton's oxidation with decolorization percentage ≈90 % which was further increased to 96.88 % and 95.23 % after aerobic treatment using two white rot fungi P. ostreatus IBL-02 (PO) and P. chrysosporium IBL-03 (PC), respectively. Mineralization efficiency was accessed by measuring the water quality assurance parameters like COD, TOC, TSS and Phenolics estimation. Reduction in COD, TOC, TSS and Phenolics were found to be 95.34 %, 90.11 %, 90.84 % and 92.22 %, respectively in two stage sequential processes. The degradation products were characterized by UV-visible and FTIR spectral techniques and their toxicity was measured. The results provide evidence that both fungal strains were able to oxidize and mineralize the selected azo dye into non-toxic metabolites.

Phanerochaete chrysosporium IBL-03 secretes high titers of manganese peroxidase during decolorization of Drimarine Blue K2RL textile dye

A novel indigenous strain, Phanerochaete chrysosporium IBL-03, with high manganese peroxidase (MnP) activities was used for decolorization of a reactive textile dye, Drimarine Blue K2R, which is used extensively in textile units of Pakistan. The initial experiment was run for seven days with 0.01% (w/v) dye solution prepared in Kirk's basal nutrient medium. Samples were removed after every 24 h and the extent of dye decolorization was determined at lambda(max) of the dye. The study revealed that P. chrysosporium caused 65% decolorization of Drimarine Blue K2RL in seven days. By process optimization, 97% colour removal could be achieved in three days using 0.005% (w/v) Drimarine Blue K2RL solution at pH 4.0 and 30 degrees C in defined Kirk's medium with 0.9% (w/v) molasses and 0.2% (w/v) ammonium dihydrogen phosphate added as carbon and nitrogen sources, respectively. Manganese peroxidase was found to be the major enzyme (560 IU/mL) involved in dye decolorization of Drimarine Blue K2RL by P. chrysosporium. The dye adsorption studies showed that the dye initially adsorbed on fungal mats disappeared later on, possibly by the action of MnP secreted by the fungus in secondary metabolism.

Improvement of fungal cellulase production by mutation and optimization of solid state fermentation

Spores of Aspergillus sp. SU14 were treated repeatedly and sequentially with Co(60) γ-rays, ultraviolet irradiation, and N-methyl-N'-nitro-N-nitrosoguanidine. One selected mutant strain, Aspergillus sp. SU14-M15, produced cellulase in a yield 2.2-fold exceeding that of the wild type. Optimal conditions for the production of cellulase by the mutant fungal strain using solid-state fermentation were examined. The medium consisted of wheat-bran supplemented with 1% (w/w) urea or NH(4)Cl, 1% (w/w) rice starch, 2.5 mM MgCl(2), and 0.05% (v/w) Tween 80. Optimal moisture content and initial pH was 50% (v/w) and 3.5, respectively, and optimal aeration area was 3/100 (inoculated wheat bran/container). The medium was inoculated with 25% 48 hr seeding culture and fermented at 35℃ for 3 days. The resulting cellulase yield was 8.5-fold more than that of the wild type strain grown on the basal wheat bran medium.

The white-rot fungus Phanerochaete chrysosporium: conditions for the production of lignin-degrading enzymes

Investigating optimal conditions for lignin-degrading peroxidases production by Phanerochaete chrysosporium (P. chrysosporium) has been a topic for numerous researches. The capability of P. chrysosporium for producing lignin peroxidases (LiPs) and manganese peroxidases (MnPs) makes it a model organism of lignin-degrading enzymes production. Focusing on compiling and identifying the factors that affect LiP and MnP production by P. chrysosporium, this critical review summarized the main findings of about 200 related research articles. The major difficulty in using this organism for enzyme production is the instability of its productivity. This is largely due to the poor understanding of the regulatory mechanisms of P. chrysosporium responding to different nutrient sources in the culture medium, such as metal elements, detergents, lignin materials, etc. In addition to presenting the major conclusions and gaps of the current knowledge on lignin-degrading peroxidases production by P. chrysosporium, this review has also suggested further work, such as correlating the overexpression of the intra and extracellular proteins to the nutrients and other culture conditions to discover the regulatory cascade in the lignin-degrading peroxidases production process, which may contribute to the creation of improved P. chrysosporium strains leading to stable enzyme production.

Decolorization potential of mixed microbial consortia for reactive and disperse textile dyestuffs

Four different aerobic mixed consortia collected from basins of wastewater streams coming out of dying plants of Crescent Textile (CT), Sitara Textile (ST), Chenab Fabrics (CF) and Noor Fatima Textile (NF), Faisalabad, Pakistan were applied for decolorization of Drimarene Orange K-GL, Drimarene Brilliant Red K-4BL, Foron Yellow SE4G and Foron Blue RDGLN for 10 days using the shake flask technique. CT culture showed the best decolorization potential on all dyestuffs followed by ST, NF and CF, respectively. CT could completely decolorize all dyes within 3-5 days. ST cultures showed effective decolorization potential on Foron Yellow SE4G and Drimarene Brilliant Red K-4BL but complete color removal was achieved after 4 and 7 days, respectively. NF culture showed 100% decolorization efficiencies on Foron Yellow SE4G and Foron Blue RDGLN but it took comparatively longer time periods (5-7 days). Where as, the NF culture had decolorized only 40% and 50% of Drimarene orange and red, respectively, after 10 days. CF caused complete decolorization of Foron Blue RDGLN and Drimarene Brilliant Red K-4BL after 4 and 8 days, respectively but it showed poor performance on other two dyes.