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This study investigated the effects of surfactant additives and medium pH on mycelial morphology and exopolysaccharide (EPS) production in liquid culture of a valuable medicinal fungus Cordyceps sinensis Cs-HK1. In the medium containing 20 g l glucose and 6 g l peptone as the sole nitrogen source, the Cs-HK1 fungal mycelia formed smooth and spherical pellets about 1.8-mm mean diameter. The mycelial pellets became less uniform at pH (4.0-5.0) lower than the optimum (pH 6.0) or turned to filamentous form at higher pH (8-9). Surfactants added to the medium inhibited pellet formation, resulting in smaller and looser pellets. Tween 80 exhibited a remarkable promoting effect on EPS production, increasing the EPS yield more than twofold at 1.5% (w/v), which was most probably attributed to the stimulation of EPS biosynthesis and release from the fungal cells by Tween 80. [ABSTRACT FROM AUTHOR]

Beauvericin (BEA) is a cyclic hexadepsipeptide mycotoxin with notable phytotoxic and insecticidal activities. Fusarium redolens Dzf2 is a highly BEA-producing fungus isolated from a medicinal plant. The aim of the current study was to develop a simple and valid kinetic model for F. redolens Dzf2 mycelial growth and the optimal fed-batch operation for efficient BEA production. A modified Monod model with substrate (glucose) and product (BEA) inhibition was constructed based on the culture characteristics of F. redolens Dzf2 mycelia in a liquid medium. Model parameters were derived by simulation of the experimental data from batch culture. The model fitted closely with the experimental data over 20-50 g l glucose concentration range in batch fermentation. The kinetic model together with the stoichiometric relationships for biomass, substrate and product was applied to predict the optimal feeding scheme for fed-batch fermentation, leading to 54% higher BEA yield (299 mg l) than in the batch culture (194 mg l). The modified Monod model incorporating substrate and product inhibition was proven adequate for describing the growth kinetics of F. redolens Dzf2 mycelial culture at suitable but not excessive initial glucose levels in batch and fed-batch cultures. [ABSTRACT FROM AUTHOR]

Abstract: Fusarium redolens Dzf2, an endophytic fungal species, is a high producer of the antibiotic compound beauvericin (BEA). However, the BEA produced by the F. redolens Dzf2 fungus was retained mainly as an intracellular product. This study was to evaluate an integrated fermentation-in situ product recovery process for enhancement of BEA production in F. redolens Dzf2 myelical culture. A macroporous polystyrene resin (X-5) was selected as the sorbent and added to the mycelial culture flasks (enclosed in a nylon bag). With 2g resin added to 40ml medium in each flask in the early stationary growth phase (day 5), the volumetric BEA yield (on day 7) was increased from 194 to 265mgl−1, with 65% being adsorbed to the resin phase. With resin renewal plus glucose feeding (on day 7), the BEA production was increased even more dramatically to 400mgl−1 (on day 9), double of the yield in the batch control culture. The results show that in situ adsorption was an effective strategy for enhancing the BEA production and also facilitating its recovery in the mycelial liquid culture. [Copyright &y& Elsevier]

Abstract: This study was to identify and optimize the major culture factors for both cell growth and carotenoid biosynthesis in Xanthophyllomyces dendrorhous through statistical experiment design and data analysis. A screening test was first conducted on seven culture factors including pH and six medium components using a Plackett–Burman design, from which glucose, ammonium sulfate and pH were identified as the significant factors affecting both cell growth and carotenoid biosynthesis. These significant factors were optimized by central composite design of experiments and response surface methodology, as 34.3g/L glucose, 2.95g/L ammonium sulfate and pH 5.85 for cell growth in the culture, and 19.3g/L glucose, 0.81g/L ammonium sulfate and pH 5.19 for carotenoid accumulation in the yeast cells, respectively. Then a two-stage culture process was exercised with these optimal conditions tailored for cell growth (first stage) and carotenoid accumulation (second stage), achieving 95.8% higher volumetric yield (18.6mg/L versus 9.5mg/L in the single-stage culture) and 22.6% higher volumetric productivity (2.33mg/(Lday) versus 1.90mg/(Lday)) of total carotenoid. The medium optimization results suggest that carotenoid biosynthesis in X. dendrorhous is promoted by high C/N ratio, low carbon and nitrogen concentrations, and a slightly acidic condition when the cell growth is suppressed. [Copyright &y& Elsevier]

Abstract: This study characterizes the effects of oxygen transfer on the growth and carotenoid (astaxanthin) production of the red yeast Phaffia rhodozyma in liquid cultures. The yeast culture on a liquid medium at 20°C had a critical dissolved oxygen (DO) concentration of 10% air-saturation (0.8mg/L) and a maximum specific oxygen uptake rate of 60mg O2/gcellh. In 250-mL shake-flasks with 50ml liquid medium, poor oxygen transfer resulted in constantly lower DO level than the critical DO in the culture. Both the biomass and carotenoid yields increased with the decrease in liquid volume in flasks and the increase in shaker speed, e.g., 8.0g dw/L biomass and 7.4mg/L carotenoid with 50mL liquid at 200rpm versus 10.7g dw/L biomass and 15.5mg/L carotenoid with 20mL liquid at 250rpm. The oxygen transfer coefficient (K L a) was correlated to shaker speed (N) and liquid volume (V L) by K L a= 0.141 N 0.88 (V L /V o)−0.80 based on linear regression of experimental data (R 2 =0.997, V o =flask volume). The carotenoid yield showed a strong linear correlation with the oxygen transfer rate (R 2 =0.989). These results show that oxygen supply is crucial for carotenoid production in P. rhodozyma liquid cultures. [Copyright &y& Elsevier]

In this work, various surfactants and cosurfactants were selected to develop nanoemulsions of finger citron essential oil (FCEO). Five suitable mixtures of surfactants were obtained: Cremophor EL/1, 2-propanediol (1:1, m/m), Cremophor EL/glycerol (1:1, m/m), Tween 80/ethanol (3:2, m/m), Tween 80/PEG-400 (3:2, m/m) and Tween 80/1, 2-propanediol (3:1, m/m). These five nanoemulsions showed a good stability with average droplet sizes kept below 20 nm for at least 28 days. All of them had low polydispersity index. Antimicrobial activities of these five nanoemulsions against bacteria ( E. coli , B. subtilis and S. aureus ) and molds ( A. niger and P. citrinum ) were tested, in which the nanoemulsion with Cremophor EL enhanced the antibacterial ability. However, the antifungal activities of these nanoemulsions were weaker than expected. These developed FCEO loaded nanoemulsions have good physical stability and antibacterial activity, suggesting their potential application in food and beverage fields. [ABSTRACT FROM AUTHOR]

Abstract: Ultrasound-assisted extraction (UAE) was evaluated for isolation of polysaccharide–protein (PSP) complexes from three important medicinal mushrooms (Grifola frondosa, Coriolus versicolor and Lentinus edodes). Compared with those of conventional hot-water extraction (HWE), the PSP yield of UAE was similar with G. frondosa, notably higher with L. edodes but lower with C. versicolor, and the extraction rate of UAE was notably higher with G. frondosa and L. edodes but much lower with C. versicolor. The PSPs from all three mushrooms by UAE had higher protein but lower carbohydrate contents than those by HWE, and their molecular weight (MW) profiles exhibited an overall shift to lower MW and a major low-MW peak near 1.0kDa. All PSPs from UAE but none from HWE exhibited 3–4 distinct protein bands between 10 and 130kDa. The antioxidant activities of PSPs extracted by UAE were generally higher than those by HWE. [Copyright &y& Elsevier]

Separation of l-glutamine (l-Gln) from Gln fermentation broth by nanofiltration (NF) was investigated with NTR7450 NF membrane. The effects of various experimental parameters such as transmembrane pressure, pH and concentration of broth on the rejection of l-Gln and l-glutamate (l-Glu) showed that NTR7450 was able to effectively separate l-Gln and l-Glu when the appropriate conditions were chosen. Moreover, the rejection of l-Gln and l-Glu in a single amino acid solution was also studied with the variation of pH, concentration, and physicochemical parameters. It was demonstrated that deviations in the rejection of fermentation broth from a single l-Gln or l-Glu solution were mainly caused by the complex ionic composition of the real fermentation broth. [Copyright &y& Elsevier]

In this work, antibacterial activity of finger citron essential oil (FCEO, Citrus medica L. var. sarcodactylis) and its mechanism against food-borne bacteria were evaluated. A total of 28 components in the oil were identified by gas chromatography-mass spectrometry, in which limonene (45.36%), γ-terpinene (21.23%), and dodecanoic acid (7.52%) were three main components. For in vitro antibacterial tests, FCEO exhibited moderately antibacterial activity against common food-borne bacteria: Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Micrococcus luteus. It showed a better bactericidal effect on Gram-positive bacteria than Gram-negative. Mechanisms of the antibacterial action were investigated by observing changes of bacteria morphology according to scanning electron microscopy, time-kill analysis, and permeability of cell and membrane integrity. Morphology of tested bacteria was changed and damaged more seriously with increased concentration and exposure time of FCEO. FCEO showed a significant reduction effect on the growth rate of surviving bacteria and lead to lysis of the cell wall, intracellular ingredient leakage, and consequently, cell death. [ABSTRACT FROM AUTHOR]

Edible and medicinal fungi (mushrooms) are widely applied to functional foods and nutraceutical products because of their proven nutritive and medicinal properties. Phellinus sensu lato is a well-known medicinal mushroom that has long been used in preventing ailments, including gastroenteric dysfunction, diarrhea, hemorrhage, and cancers, in oriental countries, particularly in China, Japan, and Korea. Polysaccharides represent a major class of bioactive molecules in Phellinus s. l., which have notable antitumor, immunomodulatory, and medicinal properties. Polysaccharides that were isolated from fruiting bodies, cultured mycelia, and filtrates of Phellinus s. l. have not only activated different immune responses of the host organism but have also directly suppressed tumor growth and metastasis. Studies suggest that polysaccharides from Phellinus s. l. are promising alternative anticancer agents or synergizers for existing antitumor drugs. This review summarizes the recent development of polysaccharides from Phellinus s. l., including polysaccharide production, extraction and isolation methods, chemical structure, antitumor activities, and mechanisms of action. [ABSTRACT FROM AUTHOR]

This study demonstrates a facile, green strategy for the preparation of gold nanoparticles (AuNPs) from chloroauric acid (HAuCl 4 ) using carboxylic curdlan (Cc) as both reducing and stabilizing agent. The as-prepared AuNPs are characterized by UV–vis spectroscopy, high resolution transmission electron microscopy, X-ray diffraction, energy dispersive X-ray spectrometry and Fourier transform infrared spectroscopy. The results indicated that the particle size of the AuNPs changes with variations in the reaction time and concentrations of Cc and HAuCl 4 . The spherical AuNPs are well dispersed, exhibiting high stability even after six months storage. The carboxylic groups (COO − ) in the Cc molecules tend to adsorb and stabilize the surface of the AuNPs. The interaction between BSA and the Cc-capped AuNPs was investigated using fluorescence and circular dichroism spectroscopies. The results indicated that the BSA molecules adsorb on the surface of the AuNPs, without significant change in its helical structure even after conjugation with the AuNPs. [ABSTRACT FROM AUTHOR]