Low Concentrations Of Acetic Acid Research Articles

Role of low-concentration acetic acid in promoting cellulose dissolution

In this study, we report on a new strategy using low-concentration acetic acid (LCAA) to promote cellulose dissolution. High-molecular-weight (HMW) cotton cellulose (DP > 5000) was simply soaked in a dilute acetic acid aqueous solution (1 vol%) prior to dissolution. Using N,N-dimethylacetamide/lithium chloride as the solvent system, the dissolution of LCAA-activated cellulose was significantly improved. Material characterization results indicated that no cellulose acetylation occurred during the dissolution process and the acetic acid could be easily removed during cellulose regeneration. It was also noticed that using LCAA to activate cellulose significantly reduced the viscosity of cellulose solution and promoted the dissolution of HMW cellulose. The crystallinity of LCAA-activated cellulose was not impacted, and the molecular weight of LCAA-activated cellulose was not significantly decreased as compared to cellulose without LCAA activation. The LCAA in cellulose played a pivotal role, by enhancing the solvation of the lithium cation. As a result, the initial free chloride concentration was able to increase and interact with inter and intra molecular hydrogen bonds of cellulose. Understanding the role of LCAA in the dissolution of cellulose is of particular interest in developing a new concept to design new solvents and effective strategies for cellulose dissolution.

Dynamic investigation of microbial activity in microbial enhanced oil recovery (MEOR)

ABSTRACTThe activity of reservoir microorganism is essential to Microbial enhanced oil recovery (MEOR). This present paper investigates the relationship between the microbial activity and production performance by means of long-scale & long-term experiments. The six rounds of nutritional injection was carried out in 135 days. During the microbial flooding experiment was performed recovering additional oil (10.44% Original Oil in Place, OOIP) after first water flooding. There is a positive correlation between water content and shannon index. And the fourth round of nutritional injection causes a considerable reduction in water content, while the concentration of Methyl-coenzyme reductase subunit alpha (mcrA) reaches peak value. In microbial flooding and reference water flooding, the concentration of mcrA maintained higher level with the low concentration of acetic acid. There are intimate correlation between water content and mcrA concentration & bacterial diversity (shannon index), which can be consider the symbol to guide the MEOR filed test.

Enhancement of lipid accumulation by oleaginous yeast through phosphorus limitation under high content of ammonia

Low concentrations of acetic acid were used as carbon source to cultivate Cryptococcus curvatus MUCL 29819 for lipid production under high content of ammonia. Phosphorus limitation combined with initial pH regulation (pH = 6) weakened inhibition of free ammonia and promoted lipid accumulation. In batch cultivation, the produced lipid content and yield was 30.3% and 0.92 g/L, higher than those under unlimited condition (18.3% and 0.64 g/L). The content of monounsaturated fatty acid also increased from 37.3% (unlimited condition) to 45.8% (phosphorus-limited condition). During sequencing batch cultivation (SBC), the lipid content reached up to 51.02% under phosphorus-limited condition while only 31.88% under unlimited condition, which can be explained by the higher conversion efficiency of the carbon source to lipid. The total energy consumption including lipid extraction, transesterification and purification was 7.47 and 8.33 GJ under phosphorus-limited and unlimited condition, respectively.

Metal-Organic Frameworks for Cultural Heritage Preservation: The Case of Acetic Acid Removal.

The removal of low concentrations of acetic acid from indoor air at museums poses serious preservation problems that the current adsorbents cannot easily address owing to their poor affinity for acetic acid and/or their low adsorption selectivity versus water. In this context, a series of topical water-stable metal-organic frameworks (MOFs) with different pore sizes, topologies, hydrophobic characters, and functional groups was explored through a joint experimental-computational exploration. We demonstrate how a subtle combination of sufficient hydrophobicity and optimized host-guest interactions allows one to overcome the challenge of capturing traces of this very polar volatile organic compound in the presence of humidity. The optimal capture of acetic acid was accomplished with MOFs that do not show polar groups in the inorganic node or have lipophilic but polar (e.g., perfluoro) groups functionalized to the organic linkers, that is, the best candidates from the list of explored MOFs are MIL-140B and UiO-66-2CF3. These two MOFs present the appropriate pore size to favor a high degree of confinement, together with organic spacers that allow an enhancement of the van der Waals interactions with the acetic acid. We establish in this work that MOFs can be a viable solution to this highly challenging problem in cultural heritage protection, which is a new field of application for this type of hybrid materials.

Effect of kaolin silver complex on the control of populations of Brettanomyces and acetic acid bacteria in wine.

In this work, the effects of kaolin silver complex (KAgC) have been evaluated to replace the use of SO2 for the control of spoilage microorganisms in the winemaking process. The results showed that KAgC at a dose of 1g/L provided effective control against the development of B. bruxellensis and acetic acid bacteria. In wines artificially contaminated with an initial population of B. bruxellensis at 104 CFU/mL, a concentration proven to produce off flavors in wine, only residual populations of the contaminating yeast remained after 24days of contact with the additive. Populations of acetic bacteria inoculated into wine at concentrations of 102 and 104CFU/mL were reduced to negligible levels after 72h of treatment with KAgC. The antimicrobial effect of KAgC against B. bruxellensis and acetic bacteria was also demonstrated in a wine naturally contaminated by these microorganisms, decreasing their population in a similar way to a chitosan treatment. Related to this effect, wines with KAgC showed lower concentrations of acetic acid and 4-ethyl phenol than wines without KAgC. The silver concentration from KAgC that remained in the finished wines was below the legal limits. These results demonstrated the effectiveness of KAgC to reduce spoilage microorganisms in winemaking.

Probiotic potential of yeasts isolated from pineapple and their use in the elaboration of potentially functional fermented beverages

Pineapple (Ananas comosus (L.) Merril) is a tropical fruit rich in nutrients characterized by a pleasant taste and widely consumed in several countries. It is used to produce juice, jams and wine. In this work, 150 yeasts isolates were obtained from peel (18) and spontaneously fermented pineapple pulp (132). The probiotic potential of 50 isolates was studied. Survival at pH 2.0, pepsin 3.0 g/L, and tolerance of bile salts (0.1 and 1% (w/v) were determined as indicators of survival potential of the isolates during the passage through the human gastrointestinal tract in simulated conditions. The selected isolates were also evaluated for their resistance to 6 antibiotics, antimicrobial activity against 6 pathogenic bacteria and autoaggregation and hydrophobicity properties. Five of them survived to gastrointestinal conditions, showed antibiotic resistance and autoaggregation properties. They were identified by MALDI-TOF MS and sequencing of ITS region as Candida lusitaniae (3) and Meyerozyma caribbica (2). Among these isolates, M. caribbica 9 D was evaluated in the production of a fermented pineapple beverage. The Saccharomyces cerevisiae var. boulardii was used as control, due to the fact that it is the only commercially available probiotic yeast. With M. caribbica inoculum, the beverage produced showed higher concentrations of residual glucose (24.19 g/L) and fructose (8.67 g/L), lower concentration of acetic acid (0.22 g/L); higher total phenolic compounds (196.93 mg/L), catechin (155.56 mg/L), chlorogenic acid (3.64 mg/L), vanillin (0.18 mg/L) and ferulic acid (33.2 mg/L). It was observed that M. caribbica population remained stable during refrigerated storage with cell counts greater than 7.00 log CFU/mL over 21 days. Compared to beverage produced with S. cerevisiae var. boulardii, the one produced with M. caribbica presented greater acceptance in the sensorial analysis for taste, aroma and general acceptance. The fermented pineapple beverage prepared with M. caribbica proved to be a good alternative in development of a potential probiotic beverage with different sensory and nutritional properties.

Impacts of diarrhea on the immune system, intestinal environment, and expression of PGRPs in New Zealand rabbits.

Diarrhea is a syndrome of digestive disorders in young rabbits and may lead to secondary infections resulting in reduced immunity and higher mortality in baby rabbits, with serious impacts on rabbit farming. In this study, we investigated the effects of diarrhea on the health of baby rabbits in terms of intestinal mucosal development, immune function, and intestinal microbial diversity. We found that the duodenal villus length and the villus/crypt ratio in rabbits with diarrhea were significantly reduced compared with those in healthy rabbits (P < 0.01). Rabbits with diarrhea had significantly lower concentrations of acetic acid (P < 0.05), higher pH levels (P < 0.05), and higher levels of ammonia nitrogen (P < 0.01) in the cecum. Moreover, diarrhea in baby rabbits led to significantly reduced levels of total serum protein (P < 0.05) and markedly increased levels of alkaline phosphatase, urea nitrogen, TNF-α, and IL-6 (P < 0.05). Transcriptional analysis of peptidoglycan recognition proteins (PGRPs, including PGLYRP-1, PGLYRP-2, and PGLYRP-3) using real-time PCR revealed that diarrhea induced the upregulation of PGRPs in the cecum and duodenum. Furthermore, through pyrosequencing of the 16S rRNA V4 region in cecum samples, we found that the total number and diversity of microbes were not significantly different between healthy rabbits and those with diarrhea, though there were noticeable differences in the prevalences of Clostridium, Roseburia, and Alistipes. Our results will contribute to a better understanding of the pathological mechanisms of diarrhea in young rabbits.

Preparation of Silica-Alumina Nanoparticles via Blast-Furnace Slag Dissolution in Low-Concentration Acetic Acid for Carbonation

Blast-furnace slag (BFS) has been used as a feedstock for CO2 sequestration by indirect mineral carbonation to produce calcium carbonate precipitates and solid residues. The most-abundant elements in these residues, Si and Al, are usually considered to be impurities that need to be removed in acid-dissolution processes involving BFS. The co-production of value-added materials from these residues is an attractive option for strengthening the economic competitiveness of mineral carbonation methods. In view of this, we separated the Si and Al, as their hydrated forms, during the dissolution of BFS in acetic acid prior to carbonation. During the sol-gel processing of Si-Al nanoparticles, a catalyst is usually required during the hydrolysis and subsequent condensation processes. In this study, only condensation occurs because the low-concentrations of acetic acid used facilitate in-situ hydrolysis during the dissolution process. Aging was carried out not only to structurally arrange the Si and Al but also to oxidize the marginal Fe(II) to reddish Fe(III). Silica-alumina nanoparticles (78% Si and 22% Al) were prepared by a simple sol-gel route at ambient pressure. These nanoparticles were amorphous and below 20 nm in size. Fourier-transform infrared (FT-IR) studies reveal that the nanoparticles consist of Si–O–Si and Si–O–Al bonds. 27Al nuclear magnetic resonance (NMR) spectroscopy reveals a significant resonance corresponding to tetra-coordinated Al inside the particle framework.

Acetic acid mediated leaching of metals from lead-free solders

BackgroundThe replacement of lead (Pb)-bearing solders by several Pb-free solders is a subject of intense research in these days due to the toxic effects of Pb on the environment. However, the Pb-free solders contain metals such as silver (Ag), copper (Cu), and zinc (Zn). The increasing use of these Pb-free solders again increases the risk of release of Ag, Cu, and Zn metals into the environment. The Pb-free solders can, therefore, be used as a secondary source for the metals which will not only help in environmental protection but also for the resource recovery.ResultsThis study reports a process to leach metals from hazardous soldering materials by acetic acid. Acetic acid was found more effective for metal recovery from the tin–copper (Sn–Cu) solder than tin–copper–silver (Sn–Cu–Ag) solder. Various process parameters were optimized for recovery of metals from Sn–Cu solder. It required 30 h for 100% recovery of Cu and Sn, respectively. The metal recovery increased gradually with an increase in acid concentration approaching complete recovery at an acid concentration of 80%. Effect of shaking speed and temperature on the recovery of metals from Sn–Cu solder was studied. The metal recovery decreased with an increase in solder weight.ConclusionThe present study reveals an effective process to recycle the Pb-free solders. The low concentration of acetic acid was also found significant for metal leaching from solder. The research provides basic knowledge for recovery of metals from Pb-free solders.

Effects of Experimental Parameters on the Extraction of Silica and Carbonation of Blast Furnace Slag at Atmospheric Pressure in Low-Concentration Acetic Acid

Blast furnace slag (BFS), a calcium-rich industrial byproduct, has been utilized since 2005 as a mineral carbonation feedstock for CO2 sequestration, producing calcium carbonate precipitates. In this study, the conditions for the dissolution of Ca and Si in acetic acid, and subsequent carbonation, were elaborated. For this purpose, the retardation of the polymerization of silicon was attempted by varying the concentration of acetic acid, temperature, and leaching time. An inductively coupled plasma (ICP) analysis revealed that both the Ca and Si dissolved completely within 30 min in 5% acetic acid at room temperature. This high dissolution value can be attributed to the fact that Ca was bound to O rather than to Si, as determined by X-ray photoelectron spectroscopy (XPS). The use of CO2-absorbed monoethanolamine enabled the complete carbonation of BFS at ambient conditions without the need for a pH swing. The presence of dissolved silica was found to affect the polymorphs of the precipitated CaCO3. We believe that this process offers a simple method for manipulating the composites of products obtained by mineral carbonation diminishing the leaching residues.

Production of bio-hydrogen and methane during semi-continuous digestion of maize silage in a two-stage system

The feasibility and performance of applying a two-stage configuration for co-production of hydrogen and methane from maize silage in continuously stirred reactors was investigated under mesophilic conditions. The high organic loading used in the first-stage hydrogen producing reactor (e.g. load shock treatment) was effective at ensuring hydrogen-producing conditions, with no methanogenic activity observed for more than 60 days. A hydrogen yield of up to 53.8 NlH2/kg volatile solid (VS) was measured in the first reactor, with a hydrogen content of 33.1%. The methane yield in the second stage reactor was 133.9 NlCH4/kgVS, with a methane content of 65%. Abnormally low concentration of acetic acid and high concentrations of caproic acid were measured in the first reactor in the pH range 5–5.5, which could be explained by the presence of strains such as Clostridium kluyveri. Of the estimated total energy yield in the two-stage system, only 4% was from hydrogen production. The mixture of hydrogen and methane produced in the system (after carbon dioxide removal) is in the range recommended for use as vehicle fuel.

Optimization of the natural debittering of table olives

Olives can debitter naturally without the use of NaOH but it is a very slow process. The purpose of this work was to evaluate the influence of both temperature and chemical characteristics of brine on the oleuropein hydrolysis rate in natural table olives. Two different phases were established for natural debittering. During the first 1–2 months of brining, a low concentration of NaCl (60 g/L) and acetic acid (2 g/L) together with a low storage temperature (10 °C) were the processing conditions that promoted a rapid hydrolysis of the bitter phenol because these mild conditions facilitated the action of endogenous enzymes (β-glucosidase and esterase). Thereafter, higher concentrations and temperature of storage (140 g/L NaCl, 16 g/L acetic acid and 40 °C) favored the chemical hydrolysis of oleuropein during long term (a few months) storage. These results will contribute to the knowledge of the natural debittering of table olives and they will help processors to accelerate their elaboration methods.

Effect of acetic acid in recycling water on ethanol production for cassava in an integrated ethanol-methane fermentation process.

Recently, the integrated ethanol-methane fermentation process has been studied to prevent wastewater pollution. However, when the anaerobic digestion reaction runs poorly, acetic acid will accumulate in the recycling water. In this paper, we studied the effect of low concentration of acetic acid (≤25 mM) on ethanol fermentation at different initial pH values (4.2, 5.2 or 6.2). At an initial pH of 4.2, ethanol yields increased by 3.0% and glycerol yields decreased by 33.6% as the acetic acid concentration was increased from 0 to 25 mM. Raising the concentration of acetic acid to 25 mM increased the buffering capacity of the medium without obvious effects on biomass production in the cassava medium. Acetic acid was metabolized by Saccharomyces cerevisiae for the reason that the final concentration of acetic acid was 38.17% lower than initial concentration at pH 5.2 when 25 mM acetic acid was added. These results confirmed that a low concentration of acetic acid in the process stimulated ethanol fermentation. Thus, reducing the acetic acid concentration to a controlled low level is more advantageous than completely removing it.

Influence of molecular weight of chitosan on the microstructures and photocatalytic property of ZrO2 prepared by chitosan templates method

ZrO2 particles with different microstructure have been fabricated through an easy method with chitosan of different molecular weights as template. The chitosan of different molecular weights was obtained through synergistic degradation of raw chitosan by α-amylase and H2O2 using microwave hydrothermal method in low concentration acetic acid (1% V/V). The as-synthesized ZrO2 particles were characterized by wide-angle powder X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and N2 adsorption⿿desorption. The possible formation mechanism of ZrO2 particles with different microstructure has been proposed, and the photocatalytic activity of the as-synthesized products was assessed by monitoring the photodegradation of Rhodamine B (Rh B) under UV irradiation. Morphologies of as-synthesized ZrO2 particles changed significantly with the different molecular weight of chitosan. As the molecular weight of chitosan decreased, the morphologies of as-synthesized ZrO2 particles showed aggregate, nano-cubes, and nano-sheets, respectively. The ZrO2 particles prepared with lower molecular weight chitosan as the template showed higher photocatalytic activity. The degradation efficiency of ZrO2 with 3.1ÿ107 and 2.4ÿ104Da chitosan as template was 64.4% and 86.2%, respectively.

In vitro influence of dietary protein and fructooligosaccharides on metabolism of canine fecal microbiota.

BackgroundThe present in vitro study investigated whether the utilization of fructooligosaccharides (FOS) may influence canine fecal microbial population in presence of diets differing in their protein content and digestibility. Fresh fecal samples were collected from five adult dogs, pooled, and incubated for 24 h with the undigested residue of three diets: 1, Low protein high digestibility diet (LP HD, crude protein (CP) 229 g/kg); 2, High protein high digestibility diet (HP HD, CP 304 g/kg); 3, High protein low digestibility diet (HP LD, CP 303 g/kg) that had been previously subjected to enzymatic digestion. In the in vitro fermentation study, there were six treatments: 1) LP HD; 2) HP HD 3) HP LD; 4) LP HD + FOS; 5) HP HD + FOS; 6) HP LD + FOS. Fructooligosaccharides were added at the final concentration of 1.5 g/L. Samples of fermentation fluid were collected at 6 and 24 h of incubation.ResultsValues of pH were reduced by FOS at 6 and 24 h (P < 0.001); conversely, low protein digestibility and high dietary protein level resulted in higher pH at both sampling times (P < 0.001). At 24 h, FOS lowered ammonia (−10 %; P < 0.001) and resulted (P < 0.05) in higher concentrations of total volatile fatty acids (VFA) (+43 %), acetic acid (+14 %), propionic acid (+75 %) and n-butyric acid (+372 %). Conversely, at 24 h, low protein digestibility resulted (P < 0.01) in lower concentrations of acetic acid (−26 %), propionic acid (−37 %) and total VFA (−21 %). Putrescine concentrations were increased at 6 and 24 h of fermentation by low protein digestibility (+21 and 22 %, respectively; P < 0.05) and FOS (+18 and 24 %, respectively; P < 0.01). After 24 h of fermentation, high dietary protein level resulted in lower counts of lactobacilli and enterococci (−0.5 and −0.7 log cells/mL, respectively; P < 0.05) whereas low protein digestibility tended to increase counts of C. perfringens (+0.2 log cells/mL; P = 0.07).ConclusionsResults from the present study showed that diets rich in protein may exert negative influences on the canine intestinal ecosystem, slightly increasing the presence of ammonia and reducing counts of lactobacilli and enterococci. Moreover, the presence of poorly digestible protein resulted in lower concentrations of VFA. Conversely, administration of FOS may improve metabolism of canine intestinal microbiota, reducing ammonia concentrations and enhancing VFA production.

Development of Rapid Identification and Risk Analysis of Moniliella Spp. in Acidic Processed Foods.

The number of spoilage incidents in the food industry attributable to a species of the genus Moniliella has recently increased, but the risk of food spoilage has not yet been evaluated. The purpose of this study was to develop a method to rapidly identify high-risk species and to conduct a risk analysis study of Moniliella spp. Acetic acid resistance of M. acetoabutens and ethanol resistance of M. suaveolens were higher than for other Moniliella species. All examined strains of M. acetoabutens developed a high tolerance to acetic acid by being cultured twice in liquid media containing low concentrations of acetic acid. These findings indicate that M. acetoabutens and M. suaveolens are high-risk species for food spoilage and must be discriminated from other fungi. We developed species-specific primers to identify M. acetoabutens and M. suaveolens using the polymerase chain reaction (PCR) to amplify the D1/D2 domain of 28S rDNA. The PCR using the primer sets designed for M. acetoabutens (Mac_F1/R1) and M. suaveolens (Msu_F1/R1) was specific to the target species and did not detect other fungi involved in food spoilage or environmental contamination. This method is expected to be effective for the monitoring of raw materials and components of the food production process.

Expression of metabolic sensing receptors in adipose tissues of periparturient dairy cows with differing extent of negative energy balance

We recently showed that the mRNA expression of genes encoding for specific nutrient sensing receptors, namely the free fatty acid receptors (FFAR) 1, 2, 3, and the hydroxycarboxylic acid receptor (HCAR) 2, undergo characteristic changes during the transition from late pregnancy to lactation in certain adipose tissues (AT) of dairy cows. We hypothesised that divergent energy intake achieved by feeding diets with either high or low portions of concentrate (60% v. 30% concentrate on a dry matter basis) will alter the mRNA expression of FFAR 1, 2, 3, as well as HCAR2 in subcutaneous (SCAT) and retroperitoneal AT (RPAT) of dairy cows in the first 3 weeks postpartum (p.p.). For this purpose, 20 multiparous German Holstein cows were allocated to either the high concentrate ration (HC, n=10) or the low concentrate ration (LC, n=10) from day 1 to 21 p.p. Serum samples and biopsies of SCAT (tail head) and RPAT (above the peritoneum) were obtained at day −21, 1 and 21 relative to parturition. The mRNA abundances were measured by quantitative PCR. The concentrations of short-chain fatty acid (SCFA) in serum were measured by gas chromatography-flame ionisation detector. The FFAR1 and FFAR2 mRNA abundance in RPAT was higher at day −21 compared to day 1. At day 21 p.p. the FFAR2 mRNA abundance was 2.5-fold higher in RPAT of the LC animals compared to the HC cows. The FFAR3 mRNA abundance tended to lower values in SCAT of the LC group at day 21. The HCAR2 mRNA abundance was neither affected by time nor by feeding in both AT. On day 21 p.p. the HC group had 1.7-fold greater serum concentrations of propionic acid and lower concentrations of acetic acid (trend: 1.2-fold lower) compared with the LC group. Positive correlations between the mRNA abundance of HCAR2 and peroxisome proliferator-activated receptor γ-2 (PPARG2) indicate a link between HCAR2 and PPARG2 in both AT. We observed an inverse regulation of FFAR2 and FFAR3 expression over time and both receptors also showed an inverse mRNA abundance as induced by different portions of concentrate. Thus, indicating divergent nutrient sensing of both receptors in AT during the transition period. We propose that the different manifestation of negative EB in both groups at day 21 after parturition affect at least FFAR2 expression in RPAT.

Presence of low concentrations of acetic acid improves yeast tolerance to hydroxymethylfurfural (HMF) and furfural

BackgroundHydrolysates derived from lignocellulosic material contain a complex mix of inhibitory compounds dependant on the type of biomass and the pre-treatment process employed. These inhibitors prevent the subsequent fermentation of available sugars by yeast into ethanol. ResultsInhibitory compounds normally work synergistically to reduce metabolic output, rates of budding and viability; however, it was observed in this study that the presence of weak acids actually improved tolerance to hydroxymethyl furfural (HMF) and furfural in Saccharomyces cerevisiae. The protective role of weak acids in HMF or furfural stressed cells was only apparent with relatively low concentrations of acetic acid (20 mM), however, there was an improvement in glucose utilisation and ethanol production when compared with HMF or furfural stressed cells. Focusing on HMF stressed cells quantitative trait loci (QTL) analysis identified a region on chromosome VI related to the enhanced tolerance to HMF in the presence of acetic acid. Two genes FET5 and HAC1 located in this region were up-regulated under the combined stress of acetic acid with HMF stress and null mutants exhibited a return to HMF sensitivity. ConclusionsPresence of acetic acid helps yeast cells overcome HMF stress, QTL analysis identified two genes on a loci on chromosome VI, knocking out these genes returns the cell to HMF sensitivity.

Designing and creating Saccharomyces interspecific hybrids for improved, industry relevant, phenotypes.

To remain competitive in increasingly overcrowded markets, yeast strain development programmes are crucial for fermentation-based food and beverage industries. In a winemaking context, there are many yeast phenotypes that stand to be improved. For example, winemakers endeavouring to produce sweet dessert wines wrestle with fermentation challenges particular to fermenting high-sugar juices, which can lead to elevated volatile acidity levels and extended fermentation times. In the current study, we used natural yeast breeding techniques to generate Saccharomyces spp. interspecific hybrids as a non-genetically modified (GM) strategy to introduce targeted improvements in important, wine-relevant traits. The hybrids were generated by mating a robust wine strain of Saccharomyces cerevisiae with a wine isolate of Saccharomyces bayanus, a species previously reported to produce wines with low concentrations of acetic acid. Two hybrids generated from the cross showed robust fermentation properties in high-sugar grape juice and produced botrytised Riesling wines with much lower concentrations of acetic acid relative to the industrial wine yeast parent. The hybrids also displayed suitability for icewine production when bench-marked against an industry standard icewine yeast, by delivering icewines with lower levels of acetic acid. Additionally, the hybrid yeast produced wines with novel aroma and flavour profiles and established that choice of yeast strain impacts on wine colour. These new hybrid yeasts display the desired targeted fermentation phenotypes from both parents, robust fermentation in high-sugar juice and the production of wines with low volatile acidity, thus establishing their suitability for wine styles that are traditionally troubled by excessive volatile acidity levels.

Enhanced digestion of waste activated sludge using microbial electrolysis cells at ambient temperature

This study examined the effects of the microbial electrolysis cell (MEC) reactions on anaerobic digestion of waste activated sludge from municipal wastewater treatment under ambient temperature conditions (22–23 °C). Two lab-scale digesters, a control anaerobic digester and an electrically-assisted digester (EAD – equipped with a MEC bioanode and cathode) were operated under three solids retention times (SRT = 7, 10 and 14 days) at 22.5 ± 0.5 °C. A numerical model was also built by including the MEC electrode reactions in Anaerobic Digestion Model No.1. In experiments, the EAD showed reduced concentration of acetic acid, propionic acid, n-butyric acid and iso-butyric acid. This improved performance of the EAD is thought to be achieved by direct oxidation of the short-chain fatty acids at the bioanode as well as indirect contribution of low acetic acid concentration to enhancing beta-oxidation. The VSS and COD removal was consistently higher in the EAD by 5–10% compared to the control digester for all SRT conditions at 22.5 ± 0.5 °C. When compared to mathematical model results, this additional COD removal in the EAD was equivalent to that which would be achieved with conventional digesters at mesophilic temperatures. The magnitude of electric current in the EAD was governed by the organic loading rate while conductivity and acetic acid concentration showed negligible effects on current generation. Very high methane content (∼95%) in the biogas from both the EAD and control digester implies that the waste activated sludge contained large amounts of lipids and other complex polymeric substances compared to primary sludge.