Fungal Pellets Research Articles

Reduction of nickel content from the model solution by consortium of fungal pellets and green algae

The accumulation of Ni from the model aqueous solution (100 mg/L) by pellets of Aspergillus niger (A. niger) together with the green algae Chlorella sp., as a microbial consortium, during five days was compared. In the experiment, already formed pellets were used (5 mL A. niger conidia in Sabouraud Dextrose Broth, shaked with 200 rpm for 5 days). The experiment was carried out under static and also dynamic conditions at 25 °C. Oxidation-Reduction-Potential (ORP) and pH were measured as well in the first, third and fifth days. Microbial consortium (A. niger with Chlorella sp.) was found always more effective – reduction of the Ni content was higher 48.95 mg/L (under static conditions) and 56.45 mg/L (dynamic conditions), pH values were medium acidic (5.84 static conditions), to weak acid (6.52 dynamic conditions). Monitored ORP values were significantly reduced in the range of -309 mV up to - 385 mV in the Ni model aqueous solution, when the both microorganisms were present. This reduction was attributed to the anoxic conditions occurred when the Reactive Oxygen Species (ROS) radicals were produced by the photoactive pigments in the algae chloroplasts.

Selenite removal from wastewater using fungal pelleted airlift bioreactor.

This study investigated the removal of selenite from wastewater using the fungus Asergillus niger KP isolated from a laboratory scale inverse fluidized bed bioreactor. The effect of different carbon sources and initial selenite concentration on fungal growth, pellet formation and selenite removal was first examined in a batch system. The fungal strain showed a maximum selenite removal efficiency of 86% in the batch system. Analysis of the fungal pellets by field-emission scanning electron microscopy, field-emission transmission electron microscopy and energy-dispersive X-ray spectroscopy revealed the formation of spherical-shaped elemental selenium nanoparticles of size 65-100nm. An increase in the initial selenite concentration in the media resulted in compact pellets with smooth hyphae structure, whereas the fungal pellets contained hair like hyphae structure when grown in the absence of selenite. Besides, a high initial selenite concentration reduced biomass growth and selenite removal from solution. Using an airlift reactor with fungal pellets, operated under continuous mode, a maximum selenite removal of 94.3% was achieved at 10mgL-1 of influent selenite concentration and 72h HRT (hydraulic retention time). Overall, this study demonstrated very good potential of the fungal-pelleted airlift bioreactor system for removal of selenite from wastewater. Graphical abstract.

From three-dimensional morphology to effective diffusivity in filamentous fungal pellets.

Filamentous fungi are exploited as cell factories in biotechnology for the production of proteins, organic acids, and natural products. Hereby, fungal macromorphologies adopted during submerged cultivations in bioreactors strongly impact the productivity. In particular,fungal pellets are known to limit the diffusivity of oxygen, substrates, and products. To investigate the spatial distribution of substances inside fungal pellets, the diffusive mass transport must be locally resolved. In this study, we present a new approach to obtain the effective diffusivity in a fungal pellet based on its three-dimensional morphology. Freeze-dried Aspergillus niger pellets were studied by X-ray microcomputed tomography, and the results were reconstructed to obtain three-dimensional images. After processing these images, representative cubes of the pellets were subjected to diffusion computations. The effective diffusion factor and the tortuosity of each cube were calculated using the software GeoDict. Afterwards, the effective diffusion factor was correlated with the amount of hyphal material inside the cubes (hyphal fraction). The obtained correlation between the effective diffusion factor and hyphal fraction shows a large deviation from the correlations reported in the literature so far, giving new and more accurate insights. This knowledge can be used for morphological optimization of filamentous pellets to increase the yield of biotechnological processes.

First Report of Black Root Rot Disease on Morinda officinalis Caused by Lasiodiplodia pseudotheobromae in China

HomePlant DiseaseVol. 103, No. 10First Report of Black Root Rot Disease on Morinda officinalis Caused by Lasiodiplodia pseudotheobromae in China PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Black Root Rot Disease on Morinda officinalis Caused by Lasiodiplodia pseudotheobromae in ChinaZhangyong Dong, Yongxin Shu, Mei Luo, Weili Zhang, Xinyu Chen, Yongxin Xiao, and Meimei XiangZhangyong Dong†Corresponding authors: Z. Dong; E-mail Address: dongzhangyong@hotmail.com and M. Xiang; E-mail Address: mm_xiang@163.comhttp://orcid.org/0000-0001-7524-0226Zhongkai University of Agriculture and Engineering, Guangzhou 510225, People’s Republic of ChinaSearch for more papers by this author, Yongxin ShuZhongkai University of Agriculture and Engineering, Guangzhou 510225, People’s Republic of ChinaSearch for more papers by this author, Mei Luohttp://orcid.org/0000-0002-1950-4204Zhongkai University of Agriculture and Engineering, Guangzhou 510225, People’s Republic of ChinaSearch for more papers by this author, Weili ZhangZhongkai University of Agriculture and Engineering, Guangzhou 510225, People’s Republic of ChinaSearch for more papers by this author, Xinyu ChenZhongkai University of Agriculture and Engineering, Guangzhou 510225, People’s Republic of ChinaSearch for more papers by this author, Yongxin XiaoZhongkai University of Agriculture and Engineering, Guangzhou 510225, People’s Republic of ChinaSearch for more papers by this author, and Meimei Xiang†Corresponding authors: Z. Dong; E-mail Address: dongzhangyong@hotmail.com and M. Xiang; E-mail Address: mm_xiang@163.comZhongkai University of Agriculture and Engineering, Guangzhou 510225, People’s Republic of ChinaSearch for more papers by this authorAffiliationsAuthors and Affiliations Zhangyong Dong † Yongxin Shu Mei Luo Weili Zhang Xinyu Chen Yongxin Xiao Meimei Xiang † Zhongkai University of Agriculture and Engineering, Guangzhou 510225, People’s Republic of China Published Online:7 Aug 2019https://doi.org/10.1094/PDIS-04-19-0857-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Morinda officinalis is a wildly cultivated medicinal plant in Zhaoqing, Guangdong Province of China. The annual production of M. officinalis in Deqin county of Zhaoqing accounts for 90% of China’s total production. In 2018, a disease on M. officinalis caused significant economic losses by affecting medicinal plant quality. Symptomatic plants exhibited blackened necrotic discoloration of roots. A diseased plant was collected in June 2018 from Zhaoqing, Guangdong, surface sterilized in 75% ethanol for 1 min and then in 2% NaClO for 3 min, and rinsed three times in sterile distilled water; internal necrotic tissue was then transferred to potato dextrose agar (PDA) and incubated at 28°C for 3 days. The fungal colonies were initially white and then became green to dark green with sporulation. Some small black pellets were found on the edge of the colony cultured on PDA medium for 25 days. The morphology of black fungal pellets was examined by light microscopy. The conidia were ellipsoidal, initially hyaline, unicellular, becoming dark brown, and developing a thick wall and a central septum. Conidia measured 16.01 to 21.74 μm long and 8.83 to 11.43 μm wide (n = 60). The conidial morphology matched that of Lasiodiplodia, a member of the Botryosphaeriaceae family (Alves et al. 2008). Moreover, the internal transcribed spacer region of the ribosomal RNA was amplified by using primers ITS1 and ITS4 (White et al. 1990) and sequenced (GenBank accession no. MK090538). The 542-bp sequence was compared with the GenBank database using nucleotide BLAST, and the isolate sequence was 100% similar to the sequence of Lasiodiplodia pseudotheobromae (GenBank accession no. MH663527). The β-tubulin gene region of the ribosomal DNA was amplified by using primers T1 (O’Donnell and Cigelnik 1997) and CYLTUB1R (Crous et al. 2004) and sequenced (GenBank accession no. MK328528). The 459-bp sequence was compared with the GenBank database using nucleotide BLAST, and the isolate sequence was 100% similar to the sequence of L. pseudotheobromae (GenBank accession no. KY583260.1). On the basis of morphological characteristics and nucleotide homology, the isolate was identified as L. pseudotheobromae, a member of the Botryosphaeriaceae family. To satisfy Koch’s postulates, both roots and leaves of M. officinalis were inoculated by placing a mycelium plug from the growing margin of 7-day-old colonies upside down directly into a fresh wound. After 3 days, the root xylem of inoculated plants turned brown and gradually became dark, similar to symptoms observed in the field. The leaves also turned brown and gradually became dark brown after 4 days. The disease spots were round or nearly circular. No symptoms were observed on the control plants. The pathogen was reisolated from root lesions, and its identity was confirmed by morphological characteristics. To our knowledge, this is first report of L. pseudotheobromae causing black root rot of M. officinalis in China.The author(s) declare no conflict of interest.

A bio-functions integration microcosm: Self-immobilized biochar-pellets combined with two strains of bacteria to remove atrazine in water and mechanisms

A self-immobilization method for microorganisms was developed based on fungal pellets. Generally, pellets have some problems such as cell leakage, cell loading limitation and low mechanical strength. Therefore, biochar was applied to overcome these disadvantages. Atrazine degradable microorganism Arthrobacter sp. ZXY-2 was immobilized by Aspergillus niger Y3 pellets. After adding biochar with optimal dosage (0.006 g biochar for 0.3 g pellets with ZXY-2), the self-immobilized biomixture (SIB) removed 50 mg /L atrazine rapidly within 1 h, which was 61% higher compared to pellets without biochar. The kinetic adsorption results showed that the biosorption of biochar by pellets followed a pseudo-second-order kinetic model. The ATZ removal ability and reusability of SIB were significantly increased by biochar. The results showed that the addition of biochar could enhance the connection between ZXY-2 and pellets based carrier, and the favorable biodegradation pH of ZXY-2 changed to 6 and 10. Several analyses such as ζ-potential measurements, FTIR, XPS, SEM-EDS, and elemental analyses were performed to evaluate the mechanism of action of SIB. To enhance the ATZ degradation by single strain, Agrobacterium, sp WL-1 was isolated and added. The metabolic pathways and their function complementation were studied. Furthermore, a biomass integration model for wastewater treatment was proposed herein.

Morphologically engineered strain of Aspergillus oryzae as a cell chassis for production development of functional lipids

Cell morphology of the oleaginous fungus, Aspergillus oryzae BCC7051, was genetically engineered by disruption of non-essential genes involved in cell wall biosynthesis. Comparative phenotypic analysis of two disruptant strains defective either in α-1,3-glucan synthase 1 (ΔAoAgs1) or chitin synthase B (ΔAoChsB), and the wild type showed that the ΔAoAgs1 strain had no alterations in colonial growth and sporulation when grown on agar medium whereas the ΔAoChsB disruptant showed growth retardation and lower sporulation. However, tiny and loose pellets were found in the ΔAoAgs1 culture grown in liquid medium, where fungal pellet size was decreased by 35–50% of the wild type size. Further investigation of the ΔAoAgs1 mutant grown under stress-induced conditions, including high salt concentration, ionic strength and osmolarity, showed that its growth and development remained similar to that of the wild type. When cultivating the ΔAoAgs1 strain in a stirred-tank bioreactor, lipid production in terms of titer and productivity was significantly improved. As compared to the wild type, an increase of triacylglycerol and ergosterol contents with a proportional decrease in steryl ester content was observed in the ΔAoAgs1 strain. These results suggest that the morphologically engineered strain of A. oryzae is a robust cell chassis useful for exploitation in further production development of functional lipids with industrial significance.

Inducing perylenequinone production from a bambusicolous fungus Shiraia sp. S9 through co-culture with a fruiting body-associated bacterium Pseudomonas fulva SB1

BackgroundFungal perylenequinonoid (PQ) pigments from Shiraia fruiting body have been well known as excellent photosensitizers for medical and agricultural uses. The fruiting bodies are colonized by a diverse bacterial community of unknown function. We screened the companion bacteria from the fruiting body of Shiraia sp. S9 and explored the bacterial elicitation on fungal PQ production.ResultsA bacterium Pseudomonas fulva SB1 isolated from the fruiting body was found to stimulate the production of fungal PQs including hypocrellins A, C (HA and HC), and elsinochromes A–C (EA, EB and EC). After 2 days of co-cultures, Shiraia mycelium cultures presented the highest production of HA (325.87 mg/L), about 3.20-fold of that in axenic culture. The co-culture resulted in the induction of fungal conidiation and the formation of more compact fungal pellets. Furthermore, the bacterial treatment up-regulated the expression of polyketide synthase gene (PKS), and activated transporter genes of ATP-binding cassette (ABC) and major facilitator superfamily transporter (MFS) for PQ exudation.ConclusionsWe have established a bacterial co-culture with a host Shiraia fungus to induce PQ biosynthesis. Our results provide a basis for understanding bacterial–fungal interaction in fruiting bodies and a practical co-culture process to enhance PQ production for photodynamic therapy medicine.

Influence of the construction of porous spargers on lovastatin production by Aspergillus terreus ATCC 20,542 in a laboratory bubble column.

In bubble column bioreactors, the hydrodynamic behavior like mixing time, bubble size and morphology of filamentous fungi are influenced by the construction of spargers. Sparger pore size is an important factor influencing formation of bubbles. In this study for the first time, a 5-L bubble column bioreactor with different porous spargers was used to investigate the effect of mean air bubble diameter (at 0.36, 0.18 and 0.09cm) on fungal growth, broth viscosity, fungal pellet morphology and lovastatin production by the filamentous fungus Aspergillus terreus. All cultivations were carried out at air flow rate equal to 0.5 Lair L-1min-1. The viscosity of the broth was influenced by both biomass concentration and size of the fungal pellets. The highest values of viscosity were observed at bubbles of 0.09cm diameter after 192h of cultivation. The largest fluffy pellets and the highest yield of lovastatin (443mg/L) were obtained at air bubbles diameter of 0.18cm. Lovastatin yield on biomass growth in this condition was, respectively, 1.7-fold and 3.5-fold higher than in the cultivations performed with air bubbles of 0.36 and 0.09cm diameters. These laboratory scale experiment indicates that air bubble diameter has the impact on lovastatin production and A. terreus culture conditions.

An X-ray microtomography-based method for detailed analysis of the three-dimensional morphology of fungal pellets.

Filamentous fungi are widely used in the production of biotechnological compounds. Since their morphology is strongly linked to productivity, it is a key parameter in industrial biotechnology. However, identifying the morphological properties of filamentous fungi is challenging. Owing to a lack of appropriate methods, the detailed three-dimensional morphology of filamentous pellets remains unexplored. In the present study, we used state-of-the-art X-ray microtomography (µCT) to develop a new method for detailed characterization of fungal pellets. µCT measurements were performed using freeze-dried pellets obtained from submerged cultivations. Three-dimensional images were generated and analyzed to locate and quantify hyphal material, tips, and branches. As a result, morphological properties including hyphal length, tip number, branch number, hyphal growth unit, porosity, and hyphal average diameter were ascertained. To validate the potential of the new method, two fungal pellets were studied-one from Aspergillus niger and the other from Penicillium chrysogenum. We show here thatµCT analysis is a promising tool to study the three-dimensional structure of pellet-forming filamentous microorganisms in utmost detail. The knowledge gained can be used to understand and thus optimize pellet structures by means of appropriate process or genetic control in biotechnological applications.

Characterization of a mycelial fructosyltransferase from Aspergillus tamarii NKRC 1229 for efficient synthesis of fructooligosaccharides

An efficient system for biotransformation of sucrose to fructooligosaccharides (FOS) was obtained using Aspergillus tamarii NKRC 1229 mycelial fructosyltransferase (m-FTase). Zymographic analysis confirmed mycelial localization of the FTase (36 U/g) and lyophilized fungal pellets were used for bioconversion. m-FTase had molecular weight ∼75 kDa with optimum activity at pH 7.0 and 20 °C. FOS production after parametric optimization (sucrose − 50% w/v, m-FTase dose − 4.5% w/v, inoculum age − 48 h and incubation time − 24 h) reached 325 g/L (55% yield) with 14% residual sucrose, 25% glucose and 6% fructose. FTase activity was enhanced after pre-treatment with organic solvents and SDS. FOS was purified in a single step using gel filtration matrix, Bio-Gel P2. FOS was characterized using Diffusion ordered spectroscopy-Nuclear Magnetic Resonance (1H DOSY-NMR) and Fourier-transform infrared spectroscopy (FTIR). Continuous generation of FOS was achieved using recyclable mycelia upto 10 consecutive cycles.

Application of Aluminum Oxide Nanoparticles in Aspergillus terreus Cultivations: Evaluating the Effects on Lovastatin Production and Fungal Morphology.

Aluminum oxide nanoparticles were supplemented to Aspergillus terreus ATCC 20542 precultures and the outcomes of the process were evaluated relative to the results of microparticle-enhanced and standard cultivations. The selected morphological parameters of fungal pellets (projected area, elongation, convexity, and shape factor) were monitored throughout the experiment, together with biomass, lactose, and lovastatin concentration. The qualitative and quantitative chemical analysis was performed with the use of liquid chromatography coupled with high resolution mass spectrometry. The results of the study indicated that the application of nanoparticles was indeed associated with morphological consequences, most notably the decreased pellet size. However, it turned out that the term “nanoparticle-enhanced cultivation” could not be used in the context of lovastatin production, as no marked increase of product titer was observed in nanoparticle-influenced variants relative to standard and microparticle-enhanced cultivation. In addition, the concentration of biomass in the nanoparticle-influenced runs was relatively low. Comparative analysis of total ion chromatograms revealed the presence of a molecule of unknown structure that could be detected solely in broths from standard and microparticle-containing cultures. This study represents the first evaluation of nanoparticles as the tools of morphological engineering aimed at enhanced lovastatin biosynthesis in A. terreus cultures.

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.

Lignocellulose integration to 1G-ethanol process using filamentous fungi: fermentation prospects of edible strain of Neurospora intermedia

BackgroundIntegration of first- and second-generation ethanol processes is one among the alternate approaches that efficiently address the current socio-economic issues of the bioethanol sector. Edible filamentous fungus capable of utilizing pentoses from lignocelluloses and also possessing biomass application as potential animal feed component was used as the fermentation strain for the integration model. This study presents various fermentation aspects of using edible filamentous fungi in the integrated first and second generation ethanol process model.ResultsFermentation of edible strain of N. intermedia on the integrated first and second-generation ethanol substrate (the mixture of dilute acid pretreated and enzymatically hydrolyzed wheat straw and thin stillage from the first-generation ethanol process), showed an ethanol yield maximum of 0.23 ± 0.05 g/g dry substrate. The growth of fungal pellets in presence of fermentation inhibitors (such as acetic acid, HMF and furfural) resulted in about 11 to 45% increase in ethanol production as compared to filamentous forms, at similar growth conditions in the liquid straw hydrolysate. Fungal cultivations in the airlift reactor showed strong correlation with media viscosity, reaching a maximum of 209.8 ± 3.7 cP and resulting in 18.2 ± 1.3 g/L biomass during the growth phase of fungal pellets.ConclusionN. intermedia fermentation showed high sensitivity to the dilute acid lignocellulose pretreatment process, with improved fermentation performance at milder acidic concentrations. The rheological examinations showed media viscosity to be the most critical factor influencing the oxygen transfer rate during the N. intermedia fermentation process. Mycelial pellet morphology showed better fermentation efficiency and high tolerance towards fermentation inhibitors.

A rapid method for harvesting and immobilization of oleaginous microalgae using pellet-forming filamentous fungi and the application in phytoremediation of secondary effluent

ABSTRACTA rapid method for harvesting and immobilization of oleaginous microalgae using pellet-forming filamentous fungi was developed. The suitable conditions for pellet formation by filamentous fungi were determined. Among the strains tested, Trichoderma reesei QM 9414 showed superior pellet forming ability. Its pellets were used to harvest oleaginous microalga Scenedesmus sp. With increasing volume ratio of fungal pellets to microalgae culture up to 1:2, >94% of microalgal cells were rapidly harvested within 10 min. The ratio of fungal pellets could manipulate both harvesting time and initial concentration of microalgal cells in the pellets. The microalgae–fungal pellets were successfully used as immobilized cells for effective phytoremediation of secondary effluent from seafood processing plants under nonsterile condition. The chemical oxygen demand, total nitrogen, and total phosphorus removal were >74%, >44%, and >93%, respectively. The scanning electron microscopy showed that the microalgal cells were not only entrapped in the pellets but also got attached to the fungal hyphae with sticky exopolysaccharides, possibly secreted by the fungi. The extracted lipids from the pellets were mainly composed of C16–C18 (>83%) with their suitability as biodiesel feedstocks. This study has shown the promising strategy to rapidly harvest and immobilize microalgal cells and the possible application in phytoremediation of industrial effluent.

Engineering fungal morphology for enhanced production of hydrolytic enzymes by Aspergillus oryzae SBS50 using microparticles.

Effect of microparticles and silver nanoparticles was studied on the production of hydrolytic enzymes by a potent phytase-producing mould, Aspergillus oryzae SBS50. Addition of microparticles, viz. talc powder and aluminum oxide enhanced phytase production from 2894 to 3903 and 2847 to 4204U/L, cellulase from 2529 to 4931 and 2455 to 3444U/L, xylanase from 9067 to 9642 and 9994 to 14,783U/L, amylase from 5880 to 11,000 and 6130 to 13,145U/L, respectively. Fungal morphology was also engineered by the use of microparticles. Fungal pellet size was significantly reduced (~ 90%) by the addition of microparticles. Fermentation time was reduced from 4 to 3 days after the addition of microparticles, thus increasing the productivity of the enzymes significantly. These results confirmed the importance of microparticles in engineering fungal morphology for enhanced production of hydrolytic enzymes.

Improved hypocrellin A production in Shiraia bambusicola by light-dark shift

Hypocrellin A (HA) is a major bioactive perylenequinone from the fruiting body of Shiraia bambusicola used for the treatment of skin diseases and developed as a photodynamic therapy (PDT) agent against cancers and viruses. The mycelial culture of S. bambusicola under dark is a biotechnological alternative for HA production but with low yield. In this study, light and dark conditions were investigated to develop effective elicitation on HA production in the cultures. Our results showed the constant light at 200 lx stimulated HA production without any growth retardation of mycelia. A light/dark shift (24: 24 h) not only increased HA content in mycelia by 65%, but stimulated HA release into the medium with the highest total HA production 181.67 mg/L on day 8, about 73% increase over the dark control. Moreover, light/dark shifting induced the formation of smaller and more compact fungal pellets, suggesting a new effective strategy for large-scale production of HA in mycelium cultures. The light/dark shift up-regulated the expression levels of two reactive oxygen species (ROS) related genes including superoxide-generating NADPH oxidase (Nox) and cytochrome c peroxidase (CCP), and induced the generation of ROS. With the treatment of vitamin C, we found that ROS was involved in the up-regulated expression of key biosynthetical genes for hypocrellins and improved HA production. These results provide a basis for understanding the influence of light/dark shift on fungal metabolism and the application of a novel strategy for enhancing HA production in submerged Shiraia cultures.

Effect of surfactants on Aspergillus brasiliensis ATCC 16404 physicochemical properties

This study investigates the adsorption of Rhamnolipid and TritonX-100 on the dense layered mycelium and hydrophobic fungi surface, A. brasiliensis to evaluate the adsorption isotherm and mechanism of the anionic and non-ionic surfactant on hydrophobic surface of fungal pellet. The mechanisms were determined by thermodynamic theory principals of surface tension and surface free energy to support the adsorption result. The change of cell surface hydrophobicity of hyphae due to surfactants adsorption was also assessed using contact angle measurements (CAM). The adsorption isotherm was fitted to Freundlich Equation with the TritonX-100 adsorbed 20% less than Rhamnolipid and shows lower Kf value. For 1 g of fungus dry weight, A. brasiliensis adsorb 1602 ± 103 μg of TritonX-100 at 0.5 CMC and at 1.0 CMC of Rhamnolipids, 1651 ± 274.8 μg of Rhamnolipids was adsorbed to successfully modify the fungi surface hydrophobicity. The CAM analysis shows A. brasiliensis became hydrophilic with respect to the concentration of both surfactants. The hydrophobic interaction was the main driving force for the adsorption of surfactants on the fungi surfaces. The present study is expected to clarify the mechanism in which surfactants influenced the aggregation of dense mycelium and provides guidelines for surfactants enhanced biodegradation using fungi.

A comparative study between fungal pellet- and spore-assisted microalgae harvesting methods for algae bioflocculation

Fungi assisted microalgae bioflocculation is an emerging, efficient and cost-effective microalgal harvesting method, but no study has systematically evaluated and compared fungal spore-assisted (FSA) and fungal pellet-assisted (FPA) microalgal harvesting methods. In this study, harvesting Chlorella sp. cells by co-culture with Penicillium sp. spores or pellets was compared. Temperature, glucose concentration, pH and fungi:algae ratio were the critical parameters for harvesting efficiency. The highest flocculation efficiency (99%) of FSA method was achieved in 28 h at 40 °C, 160 rpm, 5 g glucose/L and 1.1 × 104 cells/mL (spore). FPA method can harvest 98.26% algae cells in 2.5 h at 34 °C, 160 rpm, pH 4.0 with the fungi:algae ratio of 1:2. The carbon input for FPA is only half of that for FSA. FPA takes less time and needs less glucose input compared with FSA and may be more promising to be further developed as an effective microalgae bioflocculation method.

Fumaric Acid Production by Rhizopus oryzae ATCC® 20344™ from Lignocellulosic Syrup

Powdered activated carbon-treated lignocellulosic syrup prepared from energy cane bagasse was evaluated as a potential feedstock in the production of fumaric acid by Rhizopus oryzae ATCC® 20344™. Energy cane bagasse was pretreated with dilute ammonia and enzymatically hydrolyzed with commercially available enzymes, Cellic® CTec2 and HTec2. The collected hydrolysate samples were subjected to powdered activated carbon adsorption for the removal of non-sugar compounds (i.e., organic acids, furaldehydes, total phenolic compounds) and concentrated to a final 65°Bx syrup (mostly xylose and glucose sugars). The use of lignocellulosic syrup, the effect of nitrogen source, medium additives, and initial pH in the seed culture medium on fungal morphology were investigated. The carbon to nitrogen (C/N) ratio in the acid production medium was also optimized for maximum yields in fumaric acid production. Optimum seed culture medium conditions (2.0 g/L urea, 3.0 pH) produced the desired compact, smooth, and uniform fungal pellets. Optimum acid production medium conditions (400 C/N ratio, 0.2 g/L urea) resulted in a fumaric acid production of 34.20 g/L, with a yield of 0.43 g/g and a productivity of 0.24 g/L/h. These results were comparable to those observed with the control medium (pure glucose and xylose). The present study demonstrated that lignocellulosic syrup processed from dilute ammonia pretreated energy cane bagasse has potential as a renewable carbon source for fumaric acid fermentation by Rhizopus oryzae ATCC® 20344™.

Three dimensional typological studies using scanning electron microscopy for characterization of Termitomyces pellets obtained from submerged growth conditions

There are gaps in existing understanding of fungal pellet growth dynamics. We used scanning electron microscopy (SEM) for morphological characterization of the biomass organization of Termitomyces pellets for seven species: T. microcarpus (TMI1), T. albuminosus (TAL1, TAL2), T. striatus (TSTR), T. aurantiacus (TAUR), T. heimii (THE1, THE2), T. globulus (TGLO) and T. clypeatus (TCL1, TCL2, TCL3, TCL4, TCL5). We assessed the utility of SEM for morphological and structural characterization of Termitomyces spp. in three dimensional (3D) pellet form to identify ideal pellet morphology for industrial use. Typological classification of Termitomyces species was based on furrows, isotropy, total motifs and fractal dimensions. The pellets formed were entangled and exhibited highly compacted mycelial mass with microheterogeneity and microporosity. The mean density of furrows of Termitomyces species was between 10,000 and 11,300 cm/cm2, percentage isotropy was 30−80 and total motifs varied from 300 to 2500. TGLO exhibited the highest furrow mean density, 11243 cm/cm2, which indicated a compact, cerebroid structure with complex ridges and furrows, whereas TAL2 exhibited the lowest furrow density. TMI1a exhibited a high percentage isotropic value, 74.6, TSTR exhibited the lowest, 30.9. Total motif number also was used as a typological classification parameter. Fractal values were 2.64−2.78 for various submerged conditions of Termitomyces species. TAL1 exhibited the highest fractal dimension and TAL2 the lowest, which indicates the complexity of branching patterns. Three-dimensional SEM image analysis can provide insight into pellet micromorphology and is a powerful tool for exploring topographical details of pellets.