Showing papers on "Arabitol published in 2012"

Novel endophytic yeast Rhodotorula mucilaginosa strain PTD3 I: production of xylitol and ethanol

Abstract: An endophytic yeast, Rhodotorula mucilaginosa strain PTD3, that was isolated from stems of hybrid poplar was found to be capable of production of xylitol from xylose, of ethanol from glucose, galactose, and mannose, and of arabitol from arabinose. The utilization of 30 g/L of each of the five sugars during fermentation by PTD3 was studied in liquid batch cultures. Glucose-acclimated PTD3 produced enhanced yields of xylitol (67% of theoretical yield) from xylose and of ethanol (84, 86, and 94% of theoretical yield, respectively) from glucose, galactose, and mannose. Additionally, this yeast was capable of metabolizing high concentrations of mixed sugars (150 g/L), with high yields of xylitol (61% of theoretical yield) and ethanol (83% of theoretical yield). A 1:1 glucose:xylose ratio with 30 g/L of each during double sugar fermentation did not affect PTD3’s ability to produce high yields of xylitol (65% of theoretical yield) and ethanol (92% of theoretical yield). Surprisingly, the highest yields of xylitol (76% of theoretical yield) and ethanol (100% of theoretical yield) were observed during fermentation of sugars present in the lignocellulosic hydrolysate obtained after steam pretreatment of a mixture of hybrid poplar and Douglas fir. PTD3 demonstrated an exceptional ability to ferment the hydrolysate, overcome hexose repression of xylose utilization with a short lag period of 10 h, and tolerate sugar degradation products. In direct comparison, PTD3 had higher xylitol yields from the mixed sugar hydrolysate compared with the widely studied and used xylitol producer Candida guilliermondii.

Substrate cycles in Penicillium chrysogenum quantified by isotopic non-stationary flux analysis

Abstract: Background Penicillium chrysogenum, the main production strain for penicillin-G, has a high content of intracellular carbohydrates, especially reduced sugars such as mannitol, arabitol, erythritol, as well as trehalose and glycogen. In previous steady state 13C wash-in experiments a delay of labeling enrichments in glycolytic intermediates was observed, which suggests turnover of storage carbohydrates. The turnover of storage pools consumes ATP which is expected to reduce the product yield for energy demanding production pathways like penicillin-G. Results In this study, a 13C labeling wash-in experiment of 1 hour was performed to systematically quantify the intracellular flux distribution including eight substrate cycles. The experiments were performed using a mixed carbon source of 85% CmolGlc/CmolGlc+EtOH labeled glucose (mixture of 90% [1-13C1] and 10% [U-13C6]) and 15% ethanol [U-13C2]. It was found, that (1) also several extracellular pools are enriched with 13C labeling rapidly (trehalose, mannitol, and others), (2) the intra- to extracellular metabolite concentration ratios were comparable for a large set of metabolites while for some carbohydrates (mannitol, trehalose, and glucose) the measured ratios were much higher. Conclusions The fast enrichment of several extracellular carbohydrates and a concentration ratio higher than the ratio expected from cell lysis (2%) indicate active (e.g. ATP consuming) transport cycles over the cellular membrane. The flux estimation indicates, that substrate cycles account for about 52% of the gap in the ATP balance based on metabolic flux analysis.

Determination of carbohydrates by high performance anion chromatography-pulsed amperometric detection in mushrooms.

Abstract: A method of detecting carbohydrates (fucose, trehalose, mannitol, arabitol, mannose, glucose, galactose, fructose, and ribose) by high-performance anion chromatography-pulsed amperometric detection (HAPEC-PAD) was established. The conditions are: CarboPac MA1 column, NaOH as the eluent, temperature 30°C, Au working electrode, Ag/AgCl reference electrode, and flow rate 0.4 mL/min. These nine analytes, which yielded high resolution by this method, could be detected in 40 minutes. Mushrooms were tested and good precision, stability, and reproducibility were achieved. This method is suitable for mushroom samples and could support research and development on sugar and sugar alcohol, which contains special effects.

Optimization of arabitol production by karyoductant SP-K 7 of S. cerevisiae V30 and P. stipitis CCY 39501 using response surface methodology.

Abstract: L-arabitol is used in the food and pharmaceutical industries. It can be secreted by genetically modified Saccharomyces cerevisiae carrying the genes responsible for pentose metabolism in yeast cells. The process of the biotransformation of L-arabinose to arabitol is highly dependent on culture conditions. The aim of this investigation was to use statistical response surface methodology (RSM) for optimization of biotransformation of L-arabinose to arabitol by a karyoductant of S. cerevisiae V30 and Pichia stipitis CCY 39501, named SP-K7. Batch cultures of yeast were performed according to a Plackett-Burman design, and three factors, rotation speed, L-arabinose concentration, and temperature, were chosen for a central composite design (CCD) applied in order to optimize the production of the polyol by the karyoductant. On the basis of results obtained using 20 combinations of batch cultures of karyoductant SP-K7, the optimal levels of the factors were determined as: rotation speed 150 rpm, concentration of L-arabinose 32.5 g/l, and temperature 28 degrees C. In such conditions, the predicted concentration of arabitol after two days of incubation of SP-K7 should be 18.367 g/l. The value of R2 = 0.93195 suggested that this model was well-fitted to the experimental data. A verification of the model in experimental conditions confirmed its usefulness.

Peptone as a nitrogen source for erythritol production from glycerol by Yarrowia lipolytica yeast

Abstract: Erythritol is a compound widely distributed in nature. It found application in medicine, cosmetics, chemical and food industry. It has 60–80% sweetness in comparison to sucrose, very low energy value (~0.2 kcal/g), is non-cariogenic and free of gastric side-eff ects. Th is sugar alcohol is commercially produced in microbiological processes using glucose and sucrose. Glycerol, which is produced in large amounts by biodiesel industry, can be used as alternative substrate for the production of erythritol by Yarrowia lipolytica yeast. Th e aim of the study was to examine the impact of peptone on erythritol production from glycerol by Wratislavia K1 strain of Y. lipolytica. In the 10-days shake-fl asks experiment the peptone concentration of 1–12 g/L were examined. Pure glycerol (98% wt/wt) was used as carbon and energy source. Th e media were supplemented with 2.5% and 5% of NaCl. Th e results showed that peptone could be used as nitrogen source in erythritol biosynthesis from glycerol by Y. lipolytica yeast. Th e best results were achieved with 2 g/L of peptone and 5% of NaCl, where yeast produced 18.2 g/L of erythritol, corresponding to 0.23 g/g yield, 0.11 g/(Lh) volumetric productivity and specifi c production rate of 0.010 g/(gh). In this conditions minimal level of of by-products was formed — arabitol production was not observed while mannitol, citric acids and -ketoglutaric acid did not exceed 0.4, 4.4 and 2.0 g/L, respectively.

Method for preparing xylitol and its intermediate D-xylosone by microbial transformation of glucose and strain used in the same

Abstract: The invention discloses a method for preparing D-xylosone by microbial transformation of glucose, comprising the following steps: firstly, respectively preparing an osmophilic yeast seed liquid and a gluconobacter oxydans seed liquid by using glucose as a raw material, then inoculating the osmophilic yeast seed liquid to conduct arabitol fermentation, and then in middle and later stage inoculating the gluconobacter oxydans seed liquid to conduct mixed culture fermentation, simultaneously controlling the glucose content in the broth to be 5-10g/L, and converting arabitol into D-xylosone. According to the method, the feedback inhibition of arabitol is removed, and the efficiency of preparing D-xylosone from glucose is raised. The invention further discloses a method for preparing xylitol by microbial transformation of glucose, comprising the following steps: firstly converting glucose into D-xylosone by the above method, then converting D-xylosone into D-xylose by isomerization of enzyme, extracting and refining, and conducting catalytic hydrogenation to obtain xylitol. According to the method, the production efficiency of xylitol is raised, and the cost of preparing xylitol by biological method is reduced.