1,720,961 research outputs found
Simultaneous recovery of ferulic acid and sugars from wheat bran enzymatic hydrolysate by diananofiltration
No full textA new strategy for joint separation of ferulic acid (FA) and sugars from enzymatic hydrolysate of wheat bran was evaluated. Nanofiltration membranes with molecular weight cut-off (MWCO) in the range 150–800 g mol−1 were studied. Among them, NTR7450 and NTR7470 (Hydranautics) with MWCO between 600 and 800 g mol−1 allowed ferulic acid to be retained and sugars to permeate provided operating pH was maintained at pH > 7 and ideally pH 9. In this condition, the negative charge of the membranes and the full ionization of FA conjugate to allow FA retention by electrostatic effects whereas pore size is large enough to allow sugars to permeate. Retentions obtained on model hydrolysate at 10 bar were 85% for FA and 20% for xylose. When processing real hydrolysate, however, sugar retention was more than 40%. During diafiltration, pH decrease in the retentate was observed. Manual addition of concentrated NaOH did not allow to counterbalance completely this decrease and to ensure the optimal pH of 9 in the retentate. This led to a significative increase in sugar retention, and consequently, sugar removal in the retentate reached only 56% for a diafiltration factor Vd of 4.5. These observations were supported by a diafiltration model with variable retention
Development of a continuous biofilm-based process for the bioconversion of cheese whey into volatile fatty acids
No full textThe main goal of the present work was to study the continuous production of volatile fatty acids from a cheese whey powder in anaerobic packed bed biofilm reactors (PPBRs). Vukopor S10 ceramic cubes and granular activated carbon were employed as cell immobilization materials. Experiments were done at 37°C, pH 6. Reactors were frequently sampled for metabolites and biogas analyses. Preliminary batch tests, which were carried out in 100-mL anaerobic Pyrex bottles, demonstrated that the process consisted of two sequential phases: (a) the conversion of lactose into lactic acid and (b) the conversion of lactic acid into a mixture of VFAs. The continuous process was settled up in 1-L glass column and two different hydraulic retention times (9 and 6 days) were applied during the continuous process. Almost 80% of lactose bioconversion was achieved in Vukopor reactors, this corresponding to a 10 g/L VFAs concentration
Development of Biorefinery Schemes for the Production and Recovery of Volatile Fatty Acids from Agro-Industrial Wastes
Full text linkVolatile fatty acid (VFAs) represent the final product of anaerobic acidogenic fermentation and can be exploited as precursors for the production of added-value chemicals. The biotechnological conversion of agro-industrial wastes into VFAs can be considered a valuable alternative to waste disposal. However, the productivity of processes, which refer to the carboxylation platform are affected by the purity of produced VFAs. Biosphere SRL (Forli, Italy) had started to valorize wastes to obtain biogas.
VFAs were produced using maize silage (MS), vegetable waste (VW) and cheese whey (CW) as feedstock. The co-digestion of VW (70%) MS (30%) (VMW) under continuous operation with hydraulic retention time (HRT) of 6 days and a controlled pH 7 resulted in a VFAs rich solution of 30 g.L-1. The fermentation of CW was performed in a packed bed bioreactor where Vukuopor was the supported material. The HRT, organic loading rate (OLR) and pH were parameters tested under continuous operation. By a HRT of 6 days, ORL of 4.2 g.L-1.d-1, and pH 5.8−6, 16 g·L-1 of total VFAs were produced, with a yield higher than 75%.
Electrodialysis (ED) process was studied for the concentration of VFAs from the two acidogenic effluents resulted from the previous mentioned anaerobic acidogenic digestions. Under potentiostat operation the VMW concentration stream was concentrated from 29 g.L-1 to 50 g.L-1. Thought it is expected that a concentration of 100 g.L-1 can be achieved by performing sequential batch. With CW acidified effluent the concentration achieved was similar however the initial solution was poor in VFAs.
Experiments with Nanofiltration were performed for the separation of ferulic acid (FA) and sugars from an enzymatic hydrolysate of wheat bran. Eight different membranes were screened at different pressures and solution pH. The best condition was found be membrane NT7450 operated at pH 9 and 16 bar
Effect of operational parameters in the continuous anaerobic fermentation of cheese whey on titers, yields, productivities, and microbial community structures
Full text linkVolatile fatty acids (VFAs) were produced using cheese whey as feedstock. A mixed culture packed bed bioreactor was set up to digest anaerobically, under an acidogenic condition, a water solution of a cheese whey powder. Batch tests pointed out that the whole VFAs production process occurred via two sequential phases: (a) conversion of lactose into lactic acid and (b) conversion of lactic acid into a mixture of VFAs. Furthermore, the same tests showed that the ceramic material Vukopor S10 can be used as an effective support for cell immobilization in anaerobic fermentation processes. The effect of the hydraulic retention time (HRT) and organic loading rate (OLR) were then studied in a benchtop bioreactor operated continuously. By a HRT of 6 days, ORL of 4.2 g/L/d, and pH 5.8-6, 16 g.L-1 of total VFAs were produced, with a yield higher than 75% (Cmol(VFAs)center dot Cmol(lactose)(-1)). Characterization with Illumina-based sequencing suggested that high VFAs productivities were obtained when microbial community structures developed in the biofilm reactor were highly enriched in few genera
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Towards multi-purpose biorefinery platforms for the valorization of agro-industrial wastes: production of polyphenols, volatile fatty acids, polyhydroxyalkanoates and biogas from red grape pomace
No full textThe development of a multi-purpose four step-cascading biorefinery scheme for the valorization of red grape pomace (GP) was proposed. The consecutive processes were respectively dedicated to (a) the recovery of polyphenols by supercritical CO2 extraction, (b) the production of volatile fatty acids (VFAs) by anaerobic acidogenic digestion, (c) the exploitation of produced VFAs as the precursors for the biotechnological production of polyhydroxyalkanoates (PHAs) and (d) the production of a CH4-rich biogas by the anaerobic digestion of solid leftovers from the acidogenic process. More than 2.7 g of total polyphenols (as gallic acid equivalents) per 100 g of dry matter were extracted. A high content of valuable proanthocyanidins occurred in the recovered polyphenolic fraction. The dephenolized GP was anaerobically digested under batch acidogenic conditions, obtaining about 20 g L-1 of total VFAs in the liquid effluent. The latter matrix was employed to feed a pure culture of a Cupriavidus necator strain, which was induced to produce and store PHAs under nitrogen-limiting conditions. The process was carried out in 0.5 L-shake flasks by using a two-step production approach. In particular, pre-grown biomass was fed with different concentrations of the acidic effluent (20 or 40% v/v) in two sequential batch processes. Poly(3-hydroxybutyrate) was accumulated up to 63% of the cells dry weight when pre-grown biomass was fed with 40% of the acidic effluent. No inhibitory effects due to non-VFA compounds occurring in the actual acidogenic effluent were observed. Finally, the anaerobic digestion of the exhausted solid fraction from the acidogenic process allowed obtaining 113 mL of biomethane per gram of fed volatile solids. © The Royal Society of Chemistry 2016
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
- …
