Purification and identification of polysaccharide derived from Chlorella pyrenoidosa

The conditions for extracting and purifying polysaccharides from Chlorella pyrenoidosa, including intensity and duration of ultrasound, the temperature and incubation time, and ethanol concentration, were investigated through an orthogonal design of L₁₆(4⁵) in this work. High performance liquid chromatography (HPLC) and gas chromatography (GC) were used to characterize the compounds in C. pyrenoidosa. The highest yield of 44.8 g kg⁻¹ was achieved at 400 W of ultrasound for 800 s and then followed by incubation in water bath at 100 °C for 4 h in 80% ethanol. Two polysaccharide fractions (S1 and S2) were separated from the extracts of C. pyrenoidosa using Sepharose 4B column chromatography. The average molecular weights (M_w) of S1 and S2 were 81,877 Da and 1749 Da, respectively. Gas chromatographic (GC) traces of the hydrolyzed polysaccharides showed that most of the majority of monosaccharide in both fractions was mannose (78.0% and 76.5% of relative mass from S1 and S2, respectively) with low levels of glucose (13.2% and 8.4% of relative mass from S1 and S2, respectively). The Fourier-transform infrared spectra (FT-IR) of S1 and S2 revealed typical characteristics of polysaccharides. Both samples had the characteristics of hydroxyl groups, weak C–H band and α-pyranoses; however, only S2 had a carboxyl group.     

Astaxanthin is responsible for antiglycoxidative properties of microalga Chlorella zofingiensis

The antiglycoxidative properties of microalga Chlorella zofingiensis were investigated for the first time in this study. Algal extracts containing different contents of astaxanthin were prepared. Through the comparison, it was shown that the extract rich in astaxanthin exhibited higher antioxidant abilities as well as stronger antiglycative capacities, including the inhibition of advanced glycation endproducts (AGEs) formation, glucose autoxidation as well as glycation-induced protein oxidation. The extract was further fractionated using TLC. Among all fractions obtained, the fraction of astaxanthin in diester form was found to contain the strongest inhibitory effects on the glycation cascade. Its tentative structure was subsequently identified by LC–MS analysis. These results clearly ascertained the antiglycoxidative properties of astaxanthin derived from C. zofingiensis and supported the possibility of using natural antioxidants as glycation inhibitors. The microalga C. zofingiensis, therefore, might be the beneficial food and preventive agent choice for diabetic patients.     

Preparation,identification and their antitumor activities in vitro of polysaccharides from Chlorella pyrenoidosa

Ultrafiltration membranes of different pore size were applied to fractionate Chlorella pyrenoidosa polysaccharides (CPPS) and the main fraction could be separated by a membrane with nominal molecular weight cut-off (NMWCO) of 30 kDa. Ultrafiltration parameters of 40 °C 14.0 psi were optimized for obtaining the main fraction. The resulting sample was further purified by anion-exchange chromatography and size exclusion chromatography, and two distinctive polysaccharides, CPPS Ia and IIa were recovered. CPPS IIa had infrared spectral characteristic of polysaccharides similar to CPPS Ia, and the symmetrical stretching peak at 1408–1382 cm⁻¹ was an indication of the presence of carboxyl groups. The peak molecular weights were 69658 Da and 109406 Da, for CPPS Ia and CPPS IIa, respectively. Both CPPS Ia and IIa were composed of rhamnose, mannose, glucose, galactose and an unknown monosaccharide. Galactose (relative mass 46.5%) was the predominant monosaccharide of CPPS Ia and in CPPS IIa, rhamnose (37.8%) was predominant. CPPS Ia and IIa presented significantly higher antitumor activity against A549 in vitro than did a blank control, in a dose-dependent manner. Both fractions might be useful for developing natural safe antitumor drugs from C. pyrenoidosa resources.     

Statistical experimental design for evaluation of medium components for lipase production by Rhizopus arrhizus MTCC 2233

The Plackett-Burman experimental design was used to evaluate the medium components for lipase production by Rhizopus arrhizus in submerged batch fermentation. Twelve medium components with three dummy variables were studied in this experimental design. The most significant variables affecting lipase production were found to be olive oil, peptone, KH₂PO₄, CaCl₂·2H₂O and MgSO₄·7H₂O. Maximum lipase activity (3.98 U mL⁻¹) and maximum cell mass concentration (5.62 g L⁻¹) were obtained using the optimised medium. Unstructured kinetic models were analysed to simulate the experimental values of cell growth, lipase activity and glucose concentration. The logistic model for cell growth, the Luedeking-Piret model for lipase production and a modified Luedeking-Piret model for substrate utilisation were found to accurately predict the fermentation kinetics. The estimated values of the kinetic model parameters, α and β, for lipase production indicate that the lipase production by R. arrhizus is growth-associated.     

Water activity and temperature effects on mycotoxin production by Alternaria alternata on a synthetic tomato medium

Alternaria spp. have been reported to be the most frequent fungal species invading tomatoes. Certain species, in particular the most common one, A. alternata, are capable of producing several mycotoxins in infected plants and in agricultural commodities. Alternariol (AOH), alternariol monomethyl ether (AME), and tenuazonic acid (TA) are some of the main Alternaria mycotoxins that can be found as contaminants of food. The objective of this study was to determine the effect of water activity (a_w, 0.904, 0.922, 0.954, and 0.982) and temperature (6, 15, 21 and 35 °C) on mycotoxin production on a synthetic tomato medium of a cocktail inoculum of five strains of A. alternata isolated from tomato fruits affected by Blackmould. The optimum AOH production occurred at 0.954 a_w after 28 days of incubation at 21 °C. A temperature of 21 °C was the most favourable for AOH synthesis at all a_w levels. The maximum concentration of AME was determined at 0.954 a_w and 35 °C. The optimum conditions for TA accumulation were 0.982 a_w and 21 °C. At the 0.904 a_w no growth or germination was registered at 6 °C and 15 °C over the whole incubation period. At 21 °C and 35 °C growth occurred slowly but none of the toxins were detected at this a_w level. In general, high a_w levels were favourable for mycotoxin production. None of the other toxins was detected at quantifiable levels at 6 °C after the whole incubation period. A storage temperature of 6 °C or below could be considered as safe for tomato fruits and high moisture tomato products (a_w > 0.95), in relation with Alternaria toxins. The results obtained here could be extrapolated to evaluate the risk of spoilage in tomato fruits and tomato products caused by this pathogen.     

Effect of Capsicum carotenoids on growth and aflatoxins production by Aspergillus flavus isolated from paprika and chilli

The aim of this study was to determine the effect of a carotenoid mixture (Capsantal FS-30-NT), containing capsanthin and capsorubin, on growth and aflatoxins (AF) production of AF-producing Aspergillus flavus isolates.     

Enhanced production of isoamyl acetate from beet molasses with addition of fusel oil by Williopsis saturnus var. saturnus

Fusel oil which contains high level of amyl alcohols (approximately 45–55%) is a by-product obtained from the distillation of alcohol made by fermentation of molasses. Williopsis saturnus is a yeast which is able to convert isoamyl alcohol into isoamyl acetate. The aim of this study was to increase the formation of isoamyl acetate by the addition of fusel oil at the ratios of 1%, 2% and 3% (v/v) to molasses based fermentation medium using W. saturnus. It was found out that bioconversion of added fusel oil into isoamyl acetate was possible and an addition of 1% fusel oil led to an increase in isoamyl acetate concentration from 118 to 354 mg/L.     

Process development for mycelial growth and polysaccharide production in Tricholoma matsutake liquid culture

In this study, the effects of agitation and aeration on mycelial growth and exo-polysaccharide production were examined in batch cultures of Tricholoma matsutake. Agitation was varied from 100 to 300 rpm and aeration was varied from 0.5 to 1.5 vvm. Mycelial growth was 21.87 g/l at 150 rpm, and exo-polysaccharide production was 8.79 g/l at 1.5 vvm. When we analyzed the polysaccharide extractions from the cultured mycelium and the culture broth of T. matsutake, 1.4 g of crude polysaccharide was found per 100 g of dried weight in the cultured mycelium, and 1.47 g/l of polysaccharides was found in the culture broth. In addition, the amounts of β-Glucan in the soluble polysaccharide fractions of the cultured mycelium and culture broth were 75.4% and 83.6%, respectively. The cultured mycelium and the culture broth contained a higher amount of β-Glucan than that of the fruiting body.     

In vitro fermentation of polysaccharide from the seeds of Plantago asiatica L. by human fecal microbiota

In vitro fermentation of the polysaccharide (PLCP, Mw = 1.90 × 10⁶ Da) from seeds of Plantago asiatica L. and the contribution of its carbohydrates to the fermentation was investigated in this study. The polysaccharide was characterized by high contents of xylose, arabinose and glucuronic acid, and it was subjected to human fecal cultures to be fermented in vitro for 24 h. During fermentation, pH in fecal cultures decreased from 6.1 to 5.1 and the levels of total short-chain fatty acid (SCFA), acetic, propionic and n-butyric acids all significantly increased. Xylanase, arabinofuranosidase, xylosidase and glucuronidase activities were also improved. After 24 h incubation, 47.2 ± 1.6% of total carbohydrate in polysaccharide, including 42.9 ± 1.5% of arabinose, 53.2 ± 1.6% of xylose and 76.4 ± 1.2% of glucuronic acid, were consumed. In addition, relationship between carbohydrate consumption of the polysaccharide and SCFA production was also evaluated. It was found that the increase of acetic and n-butyric acid productions mainly resulted from the fermentation of glucuronic acid and xylose in polysaccharide, while the increase of propionic acid production was primarily due to the fermentation of arabinose and xylose. These results showed that the polysaccharide was physiologically active for human large bowel, and its carbohydrate composition determined its SCFA production.     

High-cell-density fermentation of Saccharomyces cerevisiae for the optimisation of mead production

Mead is a traditional drink that contains 8%–18% (v/v) of ethanol, resulting from the alcoholic fermentation of diluted honey by yeasts. Mead fermentation is a time-consuming process and the quality of the final product is highly variable. Therefore, the present investigation had two main objectives: first, to determine the adequate inoculum size of two commercial wine-making strains of Saccharomyces cerevisiae for the optimisation of mead fermentation; and second, to determine if an increase in yeast pitching rates in batch fermentations altered the resulting aroma profiles. Minor differences were detected in the growth kinetics between the two strains at the lowest pitching rate. With increasing pitching rates net growth of the strain ICV D47 progressively decreased, whereas for the QA23 the increasing inoculum size had no influence on its net growth. The time required to reach the same stage of fermentation ranged from 24 to 96 h depending on the inoculum size. The final aroma composition was dependent on the yeast strain and inoculum size. Fourteen of the twenty-seven volatile compounds quantified could contribute to mead aroma and flavour because their concentrations rose above their respective thresholds. The formation of these compounds was particularly pronounced at low pitching rates, except in mead fermented by strain ICV D47, at 10⁶ CFUs/mL. The esters isoamyl acetate, ethyl octanoate and ethyl hexanoate were the major powerful odourants found in the meads. The results obtained in this study demonstrate that yeast strain and inoculum size can favourably impact mead's flavour and aroma profiles.     

Submerged culture conditions for mycelial yield and polysaccharides production by Lyophyllum decastes

The effects of various carbon and nitrogen sources, their concentrations, initial pH and fermentation duration on the production of mycelia in terms of dry weight, exo-polysaccharide (EPS) and inner polysaccharide (IPS) by Lyophyllum decastes, a culinary-medicinal mushroom, were investigated in shake-flask cultures. Lactose, glucose and fructose were the top three best carbon sources for mycelial growth with corresponding yields of 6.73 g/l, 6.36 g/l and 6.10 g/l, respectively. Glucose was the best for production of EPS and IPS with 1.65 g/l and 317 mg/g dry mycelia, respectively. Maltose also performed well for EPS production. Yeast extract was the best nitrogen source for the production of mycelia (7.03 g/l) and IPS (325 mg/g dry mycelia), whereas EPS was improved further by increasing the yeast extract concentration (2.46 g/l at 2%). Similarly, initial pH 7 and 8 were best for polysaccharides production (EPS 1.73 g/l and IPS 320 mg/g) and mycelial growth (7.10 g/l), respectively. Maximum mycelial growth peaked at 15 days of cultivation whereas polysaccharides peaked at 10 days, and then tapered off. A concentration of glucose 3% and yeast extract 1% (mycelial yield and IPS) were found to be a suitable condition for submerged culture.     

Enzymatic hydrolysis of capsaicins for the production of vanillylamine using ECB deacylase from Actinoplanes utahensis

Echinocandin acylase from Actinoplanes utahensis NRRL 12052 (ECB deacylase) was used for the hydrolysis of capsaicins (trans-8-methyl-N-vanillyl-6-nonenamide and 8-methyl-N-vanillyl-6-nonanamide) into vanillylamine. Caspaicins were extracted from Capsicum annuum var. Red Cayenne. The enzyme was partially purified and used for improving molar conversion and reaction rate of the biotransformation. Under optimised conditions, the preparative biotransformation of 8.2 mM capsaicins on 200 ml scale allowed for 92% molar conversions and 59% of recovered vanillylamine.