Fungal Pellets Research Articles

Oxygen Consumption in Filamentous Pellets of Aspergillus niger: Microelectrode Measurements and Modeling.

Filamentous fungi cultivated as biopellets are well established in biotechnology industries. A distinctive feature of filamentous fungi is that hyphal growth and fungal morphology affect product titers and require tailored process conditions. Within the pellet, mass transfer, substrate consumption, and biomass formation are intricately linked to the local hyphal fraction and pellet size. This study combined oxygen concentration measurements with microelectrode profiling and three-dimensional X-ray microtomography measurements of the same fungal pellets for the first time. This allowed for the precise correlation of micromorphological information with local oxygen concentrations of two Aspergillus niger strains (hyperbranching and regular branching). The generated results showed that the identified oxygen-penetrated outer pellet regions exhibited a depth of 90-290 µm, strain-specific, with the active part percentage in the pellet ranging from 18% to 69%, without any difference between strains. Using a 1D continuum diffusion consumption model, the oxygen concentration in the pellets was computed depending on the local hyphal fraction. The best simulation results were achieved by individually estimating the oxygen-related biomass yield coefficient of the consumption term within each examined pellet, with an average estimated value of 1.95 (± 0.72) kg biomass per kg oxygen. The study lays the foundation for understanding oxygen supply in fungal pellets and optimizing processes and pellet morphologies accordingly.

Filamentous fungal pellets as versatile platforms for cell immobilization: developments to date and future perspectives

Filamentous fungi are well-known for their efficiency in producing valuable molecules of industrial significance, but applications of fungal biomass remain relatively less explored despite its abundant and diverse opportunities in biotechnology. One promising application of mycelial biomass is as a platform to immobilize different cell types such as animal, plant, and microbial cells. Filamentous fungal biomass with little to no treatment is a sustainable biomaterial which can also be food safe compared to other immobilization supports which may otherwise be synthetic or heavily processed. Because of these features, the fungal-cell combination can be tailored towards the targeted application and be applied in a variety of fields from bioremediation to biomedicine. Optimization efforts to improve cell loading on the mycelium has led to advancements both in the applied and basic sciences to understand the inter- and intra-kingdom interactions. This comprehensive review compiles for the first time the current state of the art of the immobilization of animal, yeast, microalgae, bacteria, and plant cells in filamentous fungal supports and presents outlook of applications in intensified fermentations, food and biofuel production, and wastewater treatment. Opportunities for further research and development were identified to include elucidation of the physical, chemical, and biological bases of the immobilization mechanisms and co-culture dynamics; expansion of the cell-fungus combinations investigated; exploration of previously unconsidered applications; and demonstration of scaled-up operations. It is concluded that the potential exists to leverage the unique qualities of filamentous fungus as a cellular support in the creation of novel materials and products in support of the circular bioeconomy.

Intensification and characterization of biosorption of microalgal cells on filamentous fungal pellets as effective tools for harvesting of microalgal biomass

Microalgae are promising resources with a variety of advantages and applications. However, their harvesting cost in large-scale cultivation may account for 20–30 % and in some instances up to 50 % of the overall production cost. This study then aimed to apply biosorption of microalgal cells by using fungal pellets as an alternative low-cost and practical harvesting technique. Among the fungal strains screened, Aspergillus tubingensis TSIP9 formed spherical, mycelium packed and consistent in size. The biosorption of microalgal cells process was optimized through response surface methodology (RSM). The maximum harvesting efficiency of 98.3 ± 1.2 % was achieved when using pellet loading of 60 % and pH 5.0. The biosorption process can be explained by Langmuir isotherm model with the maximum biosorption capacity (qmax) of 0.338 g/g and the Langmuir constant (K) of 0.999 L/g. Pseudo-first-order model is suitable for describing the biosorption kinetics of microalgal cells on fungal pellets. The application of fungal pellets in downstream process for microalgae cultivation was attempted. The fungal pellets could harvest microalgal cells as high as 3.70 × 1011 cells/g after 5 cycles of repeated harvesting process. FTIR analysis revealed the possible functional groups involved in fungi-microalgae interaction are CO, CO, CN, and CH. These results indicated that the potential of fungal pellets as effective tools for harvesting/immobilizing microalgal cells and their practical applications in harvesting on a large scale and resource recycling.

Microalgae-fungal pellets as novel dual-bioadsorbents for dye and their practical applications in bioremediation of palm oil mill effluent

Microalgae-fungal pellets were applied as novel dual-biosorbents for dye removal compared to fungal pellets. Both pellet types effectively removed anionic dyes better than cationic dyes, with the maximum adsorbing efficiency being nearly 100 % at a wide pH range of 3–8. The adsorption isotherms of anionic Congo Red dye and Coomassie brilliant blue R-250 dye using both pellet types and their biosorption kinetics were intensively studied. Noteworthy, the maximum adsorption capacity and affinity of microalgae-fungal pellets were much higher than those of fungal pellets. Both fungal pellets were also applied in the bioremediation of palm oil mill effluent (POME). The repeated treatment of POME by replacing pellets every 12 h enhanced the percent removal of color, phenolic compounds, and COD up to 90.97 ± 0.36 %, 70.71 ± 0.90 % and 56.55 ± 1.98 %, respectively. This study has demonstrated the promising potential for addressing dye removal and bioremediation of colored-industrial effluent in a sustainable and economically viable manner.

Application of algal-mycelial pellets in the treatment of the mariculture wastewater

Hypersaline mariculture wastewater necessitates treatment prior to its discharge into marine environments. Algal-mycelial pellets (AMPs), known for their cost-effectiveness, energy efficiency and sustainability, have not been previously explored for their flocculation and pollutant removal capabilities in hyperhaline conditions. This work employed an orthogonal test design to investigate the effects of nine factors at three levels on the treatment efficiency of mariculture wastewater using Chlorella sp. TNBR1 and Aspergillus niger AMPs. The comprehensive optimal conditions for achieving the highest flocculation efficiency and pollutant removal are determined to be a temperature of 30 °C, light intensity of 6000 lux, a 12:0 light-dark cycle, an initial pH of 6, a microalgal density of 11.25 × 106 cell/mL, microalgal growth phase at the early logarithmic stage, a fungal spore density of 9.00 × 105 spore/mL and a fungal pellet phase of 60 h. Under such conditions, the treatment of nonsterile actual mariculture wastewater with Chlorella sp. TNBR1 and Aspergillus niger AMPs results in a 93.35 %±7.20 % reduction in chemical oxygen demand (COD), 92.83 %±7.29 % reduction in total nitrogen (TN), 100 % removal of total phosphorus (TP), and a flocculation efficiency of 69.21 %±5.36 %. These findings confirm that AMPs are a viable solution for effectively treating COD, TN and TP in real hypersaline mariculture wastewater, while also facilitating the flocculation and harvesting of microalgae.

Roles of α-1,3-glucosyltransferase in growth and polysaccharides biosynthesis of Ganoderma lucidum

Ganoderma lucidum polysaccharides are valuable natural compounds possessing significant biological activity, with glycosyltransferases playing a crucial role in their biosynthesis. Although the function of β-1,3-glucosyltransferase in polysaccharides production is well understood, the role of α-1,3-glucosyltransferase in edible fungi remains unclear. In this study, over-expression of the α-1,3-glucosyltransferase gene in G. lucidum (glagt) was found to suppress the growth, with the maximum biomass and mycelial growth rate decreasing by 21.78 % and 79.61 %, respectively, a behavior distinct from β-1,3-glucosyltransferase. The fungal pellet diameter decreased by 38 % and the cell-wall thickness by 32.44 %, whereas intracellular and extracellular polysaccharides production increased by 27.58 % and 66.08 %, respectively. In the transcription level, overexpressing the glagt gene i) downregulated the citrate synthase and isocitrate dehydrogenase gene in the TCA cycle, disrupting energy metabolism and fungal growth; ii) upregulated key enzymes involved in UDP-glucose synthesis and glycosyltransferases (gl24465, gl24971, and gl22535); and iii) universally increased the transcriptional level of glucosidases gl21451, gl30087, and gl24581 by 22 %–397 %, contributing to cell-wall thinning to facilitate polysaccharides export. Conversely, the glagt gene downregulation promoted G. lucidum growth and decreased polysaccharides production. The results elucidate the roles of GLAGT and are expected to inspire in-depth exploration of polysaccharides biosynthesis pathways.

3D imaging and analysis to unveil the impact of microparticles on the pellet morphology of filamentous fungi.

Controlling the morphology of filamentous fungi is crucial to improve the performance of fungal bioprocesses. Microparticle-enhanced cultivation (MPEC) increases productivity, most likely by changing the fungal morphology. However, due to a lack of appropriate methods, the exact impact of the added microparticles on the structural development of fungal pellets is mostly unexplored. In this study synchrotron radiation-based microcomputed tomography and three-dimensional (3D) image analysis were applied to unveil the detailed 3D incorporation of glass microparticles in nondestructed pellets of Aspergillus niger from MPEC. The developed method enabled the 3D analysis based on 375 pellets from various MPEC experiments. The total and locally resolved volume fractions of glass microparticles and hyphae were quantified for the first time. At increasing microparticle concentrations in the culture medium, pellets with lower hyphal fraction were obtained. However, the total volume of incorporated glass microparticles within the pellets did not necessarily increase. Furthermore, larger microparticles were less effective than smaller ones in reducing pellet density. However, the total volume of incorporated glass was larger for large microparticles. In addition, analysis of MPEC pellets from different times of cultivation indicated that spore agglomeration is decisive for the development of MPEC pellets. The developed 3D morphometric analysis method and the presented results will promote the general understanding and further development of MPEC for industrial application.

Improved productivity and dye removal performance of Trametes versicolor pellets using rice husk as a co-substrate

Pellet production represents a critical step for several processes requiring fungal biomass, nevertheless, its optimization is seldom reported. The use of finely ground rice husk as a microcarrier and co-substrate permitted a marked increase (≈ 2.7×) in the productivity of fungal pellet production using Trametes versicolor compared to traditional production methods. The pellets show similar structure and smaller size compared to typical sole-mycelium pellets, as well as comparable laccase activity. The efficiency of the pellets for biodegradation was confirmed by the removal of the crystal violet dye, achieving significantly faster decolorization rates compared to the traditionally produced pellets. The use of these pellets during the continuous treatment of the dye in a stirred tank bioreactor resulted in 97% decolorization operating at a hydraulic residence time of 4.5 d.

Bioproduction of high-value raspberry ketone by submerged fermentation of Nidula niveo-tomentosa

Raspberry ketone (RK) is a high-value bioactive component in the growing demand for natural compounds in food and flavour industries. However, limited production persists due to low-yield microorganisms and complex biosynthetic pathway. Here, an Nidula niveo-tomentosa fungi-based fermentation system was developed to investigate and optimize the cultivation parameters for natural RK production. While optimizing glucose and phenylalanine concentrations ensured sufficient substrate supply, it unexpectedly induced stress on the substrates. Despite having minimal impact on biomass growth, UV-A radiation effectively boosted RK biosynthesis, but also reaching a ceiling with extended exposure times. Younger precultures exhibited higher specific productivity, older cultures ultimately yielded more RK due to their higher inoculum concentration. Mycelial fungi, compared to fungal pellets, outperformed in RK production, likely facilitated by enhanced nutrient uptake and bioproduct transport. Ultimately, the combination of optimized parameters unlocked a peak RK yield of 154.4 mg/L, underscoring the remarkable potential for natural RK production.

Flow modeling and structural characterization in fungal pellets

Fungal pellets are hierarchical systems that can be found in an ample variety of applications. Modeling transport phenomena in this type of systems is a challenging but necessary task to provide knowledge-based processes that improve the outcome of their biotechnological applications. In this work, an upscaled model for total mass and momentum transport in fungal pellets is implemented and analyzed, using elements of the volume averaging and adjoint homogenization methods departing from the governing equations at the microscale in the intracellular and extracellular phases. The biomass is assumed to be composed of a non-Newtonian fluid and the organelles impervious to momentum transport are modeled as a rigid solid phase. The upscaled equations contain effective-medium coefficients, which are predicted from the solution of adjoint closure problems in a three-dimensional periodic domains representative of the microstructure. The construction of these domains was performed for Laccaria trichodermophora based on observations of actual biological structures. The upscaled model was validated with direct numerical simulations in homogeneous portions of the pellets core. It is shown that no significant differences are observed when the dolipores are open or closed to fluid flow. By comparing the predictions of the average velocity in the extracellular phase resulting from the upscaled model with those from the classical Darcy equation (i.e., assuming that the biomass is a solid phase) the contribution of the intracellular fluid phase was evidenced. This work sets the foundations for further studies dedicated to transport phenomena in this type of systems.

Rapid cultivation of aerobic granular sludge for shale gas flowback water treatment by bioaugmentation with inoculating multifunctional fungal pellets

Aerobic granular sludge (AGS) technology showed great potentials in treatment of hypersaline industrial wastewater such as shale gas flowback water (SGFW), while long start-up period was still a major bottleneck. To both strengthen its granulation and pollutant removal efficiency, herein, one multifunctional fungus Aspergillus sydowii NCSL-XY1 was first isolated with the capacities including formation of fungal pellets, salt tolerance, and efficient degradation of organics in SGFW. Subsequently, its appropriate fungal pellets were used to try to shorten the start-up period of AGS in SGFW. The results showed that inoculating fungal pellets evidently accelerated the formation of AGS from 41 to 16 days. Also, it could enhance the TOC removal from ∼30% to ∼45% in the initial start-up period (Day 2-Day 11). Mechanisms analysis showed that the inoculation of fungal pellets increased EPS secretion and microbial community diversity. When the reactor stabilized, both of the AGS in R1 and R2 had similar D50 (∼1200 μm), SVI30 (∼30 mL/g), and SVI30/SVI5 (∼0.95). Also, the TOC and PAM removal in R1 and R2 were also similar and maintained at ∼71% and ∼20%. Overall, the inoculated fungal pellets played significant roles of both biomass carrier and synergistic degrader in facilitation of AGS start-up, while it had limited functions after the granules maturation. This study provided a universally effective bioaugmentation mode (screening degrading fungus and inoculating its fungal pellets) for AGS cultivation in treatment of refractory industrial wastewater.

Breaking down barriers: comprehensive functional analysis of the Aspergillus niger chitin synthase repertoire

BackgroundMembers of the fungal kingdom are heterotrophic eukaryotes encased in a chitin containing cell wall. This polymer is vital for cell wall stiffness and, ultimately, cell shape. Most fungal genomes contain numerous putative chitin synthase encoding genes. However, systematic functional analysis of the full chitin synthase catalogue in a given species is rare. This greatly limits fundamental understanding and potential applications of manipulating chitin synthesis across the fungal kingdom.ResultsIn this study, we conducted in silico profiling and subsequently deleted all predicted chitin synthase encoding genes in the multipurpose cell factory Aspergillus niger. Phylogenetic analysis suggested nine chitin synthases evolved as three distinct groups. Transcript profiling and co-expression network construction revealed remarkably independent expression, strongly supporting specific role(s) for the respective chitin synthases. Deletion mutants confirmed all genes were dispensable for germination, yet impacted colony spore titres, chitin content at hyphal septa, and internal architecture of submerged fungal pellets. We were also able to assign specific roles to individual chitin synthases, including those impacting colony radial growth rates (ChsE, ChsF), lateral cell wall chitin content (CsmA), chemical genetic interactions with a secreted antifungal protein (CsmA, CsmB, ChsE, ChsF), resistance to therapeutics (ChsE), and those that modulated pellet diameter in liquid culture (ChsA, ChsB). From an applied perspective, we show chsF deletion increases total protein in culture supernatant over threefold compared to the control strain, indicating engineering filamentous fungal chitin content is a high priority yet underexplored strategy for strain optimization.ConclusionThis study has conducted extensive analysis for the full chitin synthase encoding gene repertoire of A. niger. For the first time we reveal both redundant and non-redundant functional roles of chitin synthases in this fungus. Our data shed light on the complex, multifaceted, and dynamic role of chitin in fungal growth, morphology, survival, and secretion, thus improving fundamental understanding and opening new avenues for biotechnological applications in fungi.

Effect of pH on Trace Elements Removal from Batteries and Compact Disks by Aspergillus terreus Pellets

Background: The aim of this study is the removal of three trace elements (Nickle Ni, Cadmium Cd and Lead Pb) by an environmentally friendly method from Batteries and compact discs. This study aimed to rapidly remove trace elements from E-waste (batteries) by filamentous fungi pellets. Methods: Aspergillus was the best heavy metal tolerated isolate under the following incubation parameters: pH (5), temperature (25°C), ground electronic waste powder doses (0.5, 1 and 1.5 g/L) absorbed by fungal pellets biomass 10 gm/L of wet weight. Result: The results showed the best removal percentage R% of Ni, Cd and Pb removal were (89,91and 96) observed at pH 5. Images from SEM showed accumulations of metal particles on the surface of the fungal hyphae and Fourier Transform Infra-Red Spectroscopy (FT-IR) was used to determine the effective groups in the fungal cell wall responsible of biosorption of trace elements and This study indicates that an application may be possible Aspergillus terreus as a promising candidate for biological sorption and recycling of trace elements and as an ecologically friendly and effective process in terms of time and cost.

Fermentative processes for the upcycling of xylose to xylitol by immobilized cells of Pichia fermentans WC1507.

Xylitol is a pentose-polyol widely applied in the food and pharmaceutical industry. It can be produced from lignocellulosic biomass, valorizing second-generation feedstocks. Biotechnological production of xylitol requires scalable solutions suitable for industrial scale processes. Immobilized-cells systems offer numerous advantages. Although fungal pellet carriers have gained attention, their application in xylitol production remains unexplored. In this study, the yeast strain P. fermentans WC 1507 was employed for xylitol production. The optimal conditions were observed with free-cell cultures at pH above 3.5, low oxygenation, and medium containing (NH4)2SO4 and yeast extract as nitrogen sources (xylitol titer 79.4g/L, YP/S 66.3%, and volumetric productivity 1.3g/L/h). Yeast cells were immobilized using inactive Aspergillus oryzae pellet mycelial carrier (MC) and alginate beads (AB) and were tested in flasks over three consecutive production runs. Additionally, the effect of a 0.2% w/v alginate layer, coating the outer surface of the carriers (cMC and cAB, respectively), was examined. While YP/S values observed with both immobilized and free cells were similar, the immobilized cells exhibited lower final xylitol titer and volumetric productivity, likely due to mass transfer limitations. AB and cAB outperformed MC and cMC. The uncoated AB carriers were tested in a laboratory-scale airlift bioreactor, which demonstrated a progressive increase in xylitol production in a repeated batch process: in the third run, a xylitol titer of 63.0g/L, YP/S of 61.5%, and volumetric productivity of 0.52g/L/h were achieved. This study confirmed P. fermentans WC 1507 as a promising strain for xylitol production in both free- and entrapped-cells systems. Considering the performance of the wild strain, a metabolic engineering intervention aiming at further improving the efficiency of xylitol production could be justified. MC and AB proved to be viable supports for cell immobilization, but additional process development is necessary to identify the optimal bioreactor configuration and fermentation conditions.

Biotechnological insights into extracellular enzyme production by thermotolerant fungi from hot springs and caves: Morphology, pellets formation, and protease production.

This study investigates the thermotolerant fungal biodiversity in caves and hot springs, focusing on their potential for extracellular enzyme production, specifically proteases. Samples were collected from the Cardonal region in Hidalgo, Mexico, using three different isolation methods. The study characterizes the morphological diversity of the isolated fungi and identifies various genera, including Aspergillus, Penicillium, Trichoderma, Cladosporium, and Fusarium, based on morphology. The isolated fungi were screened for their ability to produce extracellular enzymes on solid media, with a particular emphasis on proteases due to their industrial significance. Among the 35 isolated fungi, 20 exhibited proteolytic activity, and 12 strains were identified as good protease producers based on enzymatic index values. The study also evaluated the formation of fungal pellets by proteolytic fungi and found certain strains to display significant pellet formation. Additionally, protease production was examined by fungal pellets in submerged cultures, with isolate 6 demonstrating the highest protease activity. The findings highlight the diverse thermotolerant fungal biodiversity in extreme environments, and emphasize their potential for enzymatic production. This research contributes to our understanding of fungal ecology and provides insights into the biotechnological applications of these enzymes. The study recommends further molecular investigations to enhance biodiversity studies in such extreme environments.

Fungal pellets of Pleurotus ostreatus and Rhizopus stolonifer for biotechnological applications: Characterization and production optimization using Taguchi methodology

Filamentous fungi are known for their significant potential in biotechnology, thanks to their versatile enzyme systems with various applications. However, dealing with their growth patterns and structural configurations presents significant challenges. To tackle these issues, fungal pellets are emerging as potential solutions, providing compact biomass aggregates that offer distinct advantages for bioprocesses. This study delves into characterization and optimizing pellet formation for Pleurotus ostreatus and Rhizopus stolonifer using the Taguchi methodology, aiming to enhance their biotechnological applications. By systematically varying parameters such as agitation level (AL), glucose concentration (GC), and inoculum size (IS), we identified key factors influencing pellet formation. Results indicate that P. ostreatus forms pellets in rich media from mycelium, while R. stolonifer requires a minimal medium with pH modifications for pelletization via a coagulative mechanism. The optimization process reveals that agitation level is a crucial factor for maximizing pellet production in both models, while the other factors do not seem to influence the process significantly but impact the morphology and quantity of pellets. The results suggest that by optimizing parameters using the Taguchi method, it is possible to achieve acceptable pellet formation performance in both fungi. Understanding these factors is essential for improving the efficiency of biotechnological processes involving fungal biomass, providing valuable insights into enhancing fungal pellet production for various applications.

Morphological responses of filamentous fungi to stressful environmental conditions.

The filamentous growth mode of fungi, with its modular design, facilitates fungal adaptation to stresses they encounter in diverse terrestrial and anthropogenic environments. Surface growth conditions elicit diverse morphological responses in filamentous fungi, particularly demonstrating the remarkable adaptability of mycelial systems to metal- and mineral-rich environments. These responses are coupled with fungal biogeochemical activity and can ameliorate hostile conditions. A tessellated agar tile system, mimicking natural environmental heterogeneity, revealed negative chemotropism to toxic metals, distinct extreme growth strategies, such as phalanx and guerrilla movements and transitions between them, and the formation of aggregated re-allocation structures (strands, cords, synnemata). Other systems showed intrahyphal growth, intense biomineralization, and extracellular hair-like structures. Studies on submerged mycelial growth, using the thermophilic fungus Thielavia terrestris as an example, provided mechanistic insights into the morphogenesis of two extreme forms of fungal submerged culture-pelleted and dispersed growth. It was found that the development of fungal pellets was related to fungal adaptation to unfavorable stressful conditions. The two key elements affecting morphogenesis leading to the formation of either pelleted or dispersed growth were found to be (1) a lag phase (or conidia swelling stage) as a specific period of fungal morphogenesis when a certain growth form is programmed in response to morphogenic stressors, and (2) cAMP as a secondary messenger of cell signaling, defining the implementation of the particular growth strategy. These findings can contribute to knowledge of fungal-based biotechnologies, providing a means for controllable industrial processes at both morphological and physiological levels.

Filamentous fungal pellets as a novel and sustainable encapsulation matrix for exogenous bioactive compounds.

Edible filamentous fungi (FF) are considered sustainable food materials given their rich nutrient profile and low carbon and water footprints during production. The current study evaluated FF biomass as a natural encapsulation system for exogenous bioactive compounds and as a model system to investigate the complex food matrix-micronutrient interactions during in vitro digestion. Our objective was to compare the fungal pellet, as a multicellular encapsulation system, with single yeast cell-based carriers in terms of loading and release of curcumin, a model compound. The results suggest that the curcumin encapsulation efficiency was similar in single yeast cells and fungal hyphal cells. A vacuum treatment used to facilitate the infusion of curcumin into yeast or fungal cells also enabled rapid internalization of yeast cells into the fungal pellet matrix. Compared to the single-cell encapsulation system, the multicellular systems modified the release kinetics of curcumin during in vitro digestion by eliminating the initial rapid release and reducing the overall release rate of curcumin in the small intestinal phase. These results provide a deeper understanding of the effect of natural edible structures on the bioaccessibility of micronutrients, and demonstrate the potential of using FF biomass as functional food materials.

Xenobiotic Removal by Trametes hirsuta LE-BIN 072 Activated Carbon-Based Mycelial Pellets: Remazol Brilliant Blue R Case Study

As a toxic xenobiotic compound, the anthraquinone dye Remazol Brilliant Blue R (RBBR) poses a serious threat to aquatic ecosystems. In the present study, the ability of Trametes hirsuta to remove RBBR from the medium was investigated, and the role of adsorption by fungal mycelium and biodegradation by fungal enzymes was evaluated. It was shown that the whole fungal culture was able to remove up to 97% of the dye within the first four hours of incubation. Based on enzymatic activities in the culture broth, laccases were proposed to be the main enzymes contributing to RBBR degradation, and RT-qPCR measurements demonstrated an increase in transcription for the two laccase genes—lacA and lacB. Composite mycelial pellets of T. hirsuta with improved adsorption ability were prepared by adding activated carbon to the growth medium, and the induction of laccase activity by carbon was shown. For composite pellets, the RBBR decolorization degree was about 1.9 times higher at 1 h of incubation compared to carbon-free pellets. Hence, it was shown that using fungal mycelium pellets containing activated carbon can be an effective and economical method of dye removal.

Flor yeast immobilization in microbial biocapsules for Sherry wine production: microvinification approach

Sherry wine is a pale-yellowish dry wine produced in Southern-Spain which features are mainly due to biological aging when the metabolism of biofilm-forming yeasts (flor yeasts) consumes ethanol (and other non-fermentable carbon sources) from a previous alcoholic fermentation, and produces volatile compounds such as acetaldehyde. To start aging and maintain the wine stability, a high alcohol content is required, which is achieved by the previous fermentation or by adding ethanol (fortification). Here, an alternative method is proposed which aims to produce a more economic, distinctive Sherry wine without fortification. For this, a flor yeast has been pre-acclimatized to glycerol consumption against ethanol, and later confined in a fungal-based immobilization system known as “microbial biocapsules”, to facilitate its inoculum. Once aged, the wines produced using biocapsules and free yeasts (the conventional method) exhibited chemical differences in terms of acidity and volatile concentrations. These differences were evaluated positively by a sensory panel. Pre-acclimatization of flor yeasts to glycerol consumption was not successful but when cells were immobilized in fungal pellets, ethanol consumption was lower. We believe that immobilization of flor yeasts in microbial biocapsules is an economic technique that can be used to produce high quality differentiated Sherry wines.