Highest Acetic Acid Production Research Articles

Impact of single and mixed cultures of yeasts and lactic acid bacteria in coffee fermentation and cup quality

AbstractSaccharomyces cerevisiae LBTF 21.3, Pichia manshurica LBTF 21.1, and Leuconostoc lactis LBTF 21.1 were used as single and mixed cultures in coffee fermentations. Fermentations carried out in glass jars with P. manshurica LBTF 21.1/Leuc. lactis LBTF 21.1 showed higher fermentation rates than S. cerevisiae LBTF 21.3/P. manshurica LBTF 21.1 or S. cerevisiae LBTF 21.3/Leuc. lactis LBTF 21.1. The highest cup quality was reached with P. manshurica LBTF 21.1/Leuc. lactis LBTF 21.1 (83.0 points). Full factorial design (22) carried out with P. manshurica LBTF 21.1 revealed that the higher proportion of water added before the fermentation resulted in higher production of acetic acid. A contrary effect of this variable was observed on the production of lactic acid with Leuc. lactis LBTF 21.1. Fermentations conducted in bioreactor evidenced the production of acetaldehyde by P. manshurica LBTF 21.1/Leuc. lactis LBTF 21.1, P. manshurica LBTF 21.1, and Leuc. lactis LBTF 21.1. Additionally, the highest cup quality was reached in fermentations with P. manshurica LBTF 21.1 (82.5 points) followed by Leuc. lactis LBTF 21.1 (81.5 points) and P. manshurica LBTF 21.1/Leuc. lactis LBTF 21.1 (81.0 points). Fermentations of coffee with single and mixed cultures are interesting strategies for the improvement of the sensory quality.

Formation and improvement mechanism of physical property and volatile flavor of fermented tilapia surimi by newly isolated lactic acid bacteria based on two dimensional correlation networks

Fermentation is an effective way to improve the gel properties of freshwater fish surimi. In this study, two newly isolated Lactiplantibacillus plantarum H30-2 and Pediococcus acidilactici H30-21 were used to improve the physical properties and volatile flavor of fermented tilapia surimi. L. plantarum H30-2 quickly improved the whiteness, gel strength, hardness, and chewiness within 18 h. Among 172 volatile compounds analyzed by HS-SPME-GC–MS, most pleasant core flavor compounds (OAV ≥ 1) were improved by L. plantarum H30-2. L. plantarum H30-2 could always adapt to the surimi environment while P. acidilactici H30-21 could not. Two dimensional correlation networks showed that Lactiplantibacillus and Lactococcus were responsible for the quality formation in surimi during natural fermentation or with starters, while the quality improvement after L. plantarum H30-2 addition mainly resulted from the increasing Lactiplantibacillus and its higher acetic acid production. L. plantarum H30-2 can be developed as a special starter using for tilapia surimi fermentation.

White grape variety Maraština as a promising source of non-Saccharomyces yeasts intended as starter cultures

Non-Saccharomyces wine yeasts are recognized for their ability to enhance the aroma complexity of wines. New trends in winemaking have highlighted the concept of microbiological terroir thus encouraging the use of indigenous non-Saccharomyces starter cultures in mixed fermentations with Saccharomyces cerevisiae to overcome the lack of authenticity and provide the wines with unique regional character and distinct aromatic profiles. In this study, 257 indigenous non-Saccharomyces isolates were obtained for the first time from 11 Maraština vineyards located within the winegrowing region of Dalmatia (Croatia). The isolates were identified at the molecular level and characterized for desirable oenological traits such as growth at different temperatures, high ethanol and SO2 tolerance, and for negative features such as high hydrogen sulphide (H2S) and acetic acid production as well as hydroxycinnamic acid decarboxylase (HCDC) activity. Among 27 identified species, those from Aureobasidium genera prevailed, followed by Metschnikowia, Hanseniaspora and Lachancea. The representatives from different species showed high SO2 (up to 250 mg/L) and ethanol (up to 12%) tolerance, low acetic acid, and medium-low H2S production. The HCDC activity was detected exclusively among Metschnikowia, Aureobasidium and Kabatiella species. Some regionally distinct characteristics within the isolates from the same species were observed. The encouraging insights into potential new starter cultures emerged after the evaluation of enzymatic activities of selected isolates. Most of them showed high leucine and valine arylamidase activity, whereas Hanseniaspora and Metschnikowia isolates were additionally characterized by high β-glucosidase and esterase activity, respectively.

Reduction of ethanol content in wine with an improved combination of yeast strains and process conditions

One interesting strategy to address the increasing alcohol content of wines, associated with climate change, is to reduce the ethanol yield during fermentation. Within this strategy, the approach that would allow the clearest reduction in alcohol content is the respiration of part of the grape sugars by yeasts. Non-Saccharomyces species can be used for this purpose but suffer from a limited ability to dominate the process and complete fermentation. In turn, Saccharomyces cerevisiae shows a high production of acetic acid under the growth conditions required for respiration. Previously proposed procedures used combinations of non-Saccharomyces and S. cerevisiae starters, or a strain of S. cerevisiae (PR1018), with unique metabolic properties. In both cases, precise management of oxygen availability was required to overcome the acetic acid problem. In this work, we have developed a laboratory scale process to take advantage of the properties of PR1018 and a strain of Metschnikowia pulcherrima. This process is more robust than the previous ones and does not rely on strict control of oxygenation or even the use of this particular strain of S. cerevisiae. Aeration can be interrupted instantly without impairing the volatile acidity. Under the selected conditions, an ethanol reduction of around 3% (v/v) was obtained compared to the standard fermentation control.

Schwanniomyces etchellsii, acid-thermotolerant yeasts from urban city soil

Acid-tolerant yeasts are one of the important keys to producing ethanol from acidic substrates, especially from molasses and agricultural waste. In this study, selected cultivars of yeasts isolated from a variety of locations such as botanical gardens in Thailand urban areas, which are often found highly polluted in the air such as carbon dioxide which is a cause of acid rain. There is limited information about how tolerant yeasts, are or their functional properties related to the environment. Yeast species were determined by using the18S rDNAsequence guide. The level of acid tolerance was evaluated by adding to the culture medium lactic acid (300-900mM), acetic acid (100-400mM), and propionic acid (25-100mM).18S rDNAanalysis has shown a %similarity of the nucleotide sequence higher than 98.65% compared to the database.Schwanniomyces etchellsiistrains found in urban city soil were notable for their tolerance of lactic acid up to 100mM. There are two main types of yeasts in overall acid tolerance:S. etchellsii,which is recognized as an osmotic pressure-resistant species that is highly resistant to fermentation inhibitors and produces ethanol; andSchizosaccharomyces pombe, which cell wall has been reported to be characterized by accumulation of α-(1,3)-glucan and malic acid can be used in metabolic pathways. The results show thatS. pombe, isolated from rice paddy fields, can grow efficiently in acetic and propionic acid up to 400mM and 100mM, respectively. This species could be cultured in ethanol at a concentration of 12.5% (v/v). Moreover, it presented high ethanol and acetic acid production of 14.5-15.9g/L and 7-10g/L, respectively, with or without acidic conditions. In comparison,S. etchellsii, isolated from the botanical garden soil, which is grown in acetic, propionic, and lactic acid, was also indicated to be an organic acid-tolerant species.

Development of Halotolerant Microbial Consortia for Salt Stress Mitigation and Sustainable Tomato Production in Sodic Soils: An Enzyme Mechanism Approach

Salt stress caused by sodic soils is an important constraint that impacts the production of crucial solanaceous vegetable crops globally. Halotolerant poly-extremophiles rhizobacteria can inhabit hostile environments like salinity, drought, etc. The present study was aimed to design a halotolerant micro-formulation using highly salt-tolerant bacterial strains previously isolated from salt-tolerant rice and wheat rhizosphere in sodic soil. Nine halotolerant isolates were examined for plant growth-promoting traits and biomass production in pot studies with sodic soil of pH 9.23 in tomato. Compatible, efficient isolates were aimed to be formulated into different consortia like PGPR-C1, PGPR-C2 and, PGPR-C3 for field evaluation in sodic soils of pH 9.14. Halotolerant rhizobacterial consortia (PGPR-C3) comprising Lysinibacillus spp. and Bacillus spp. were found to produce extracellular enzymes like amylase, protease, cellulase, and lipase, showing significantly enhanced vegetative parameters, yield and lycopene content of tomato hybrid NS585 under salt-stressed sodic soils. PGPR-C3 consortia also showed enhanced plant growth-promoting activities and halo tolerance like high Indole acetic acid production, 1-aminocyclopropane-1-carboxylic acid deaminase, and antioxidative enzyme activity over the uninoculated control. Further, inoculation with PGPR-C3 consortia resulted in the efficient exclusion of Na+ ions from the rhizosphere through increased absorption of K+. Results of the study reveal that inoculation with PGPR-C3 consortia could alleviate the salt stress and promotes the successful cultivation of tomato crop in sodic soils. It can be considered the best option for eco-friendly, sustainable cultivation of vegetables like a tomato in sodic soils with a high pH range of up to 9.14.

Reduced acetic acid formation using NaHSO3 as a steering agent by Actinobacillus succinogenes GXAS137.

The high production of acetic acid (AC) as a by-product leads to difficult separation and purification of succinic acid (SA) and increases production costs in SA fermentation by Actinobacillus succinogenes. NaHSO3 as a steering agent was used to reduce AC production. Herein, the optimum fermentation conditions were achieved by single-factor and orthogonal tests as follows: glucose 60g/L; MgCO3 60g/L; NaHSO3 0.15% (w/v); and NaHSO3 addition time, 8h after inoculation. After optimization, the SA and AC contents were 44.42 and 5.73g/L. The SA improved by 100.72%, the AC decreased by 21.18% compared with the unfermented. The acetate kinase activity decreased by 14.36% and acetyl-CoA content improved by 97.55% in the group of NaHSO3 addition compared with control check (CK). The mechanism of NaHSO3 is formation acetaldehyde-sodium bisulfite compound and reduction the activity of acetate kinase. These findings indicated a new way of using NaHSO3 as a steering agent to reduce AC generation and may help promote the development of SA industrial production.

Proteolytic activity under white wine fermentation by Hanseniaspora vineae yeast strains

Apiculate yeasts from Hanseniaspora genus are predominant on the native flora of grapevines, while Hanseniaspora uvarum is well known for its abundant presence in grapes, it results generally, in detrimental quality effects on wine due to high production of acetic acid. By contrast, Hanseniaspora vineae is better adapted to fermentation, increasing flavor complexity in wines as it has been demonstrated in winemaking practices during the last decade. We obtained a collection of more than 22 different Hanseniaspora vineae strains from which we could detect, by a plating screening method, high and moderate protease activity. In this study, we tested these strains under real winemaking conditions on a Sauvignon blanc white wine must. Results obtained demonstrated that there is an interesting protease active diversity in all H. vineae strains when compared to conventional fermentations conducted by Saccharomyces cerevisiae. Four H. vineae strains showed a decrease in wine protein turbidity, up to three times lower than that observed in S. cerevisiae, which imply a significant decrease in the demand for bentonite before bottling. This attribute of some H. vineaestrains should be very attractive at the commercial level to reduce manipulations and flavor removal in the production of delicate white wines such as Sauvignon blanc.

Bacillus velezensis strain Ag75 as a new multifunctional agent for biocontrol, phosphate solubilization and growth promotion in maize and soybean crops

Soybean and maize are some of the main drivers of Brazilian agribusiness. However, biotic and abiotic factors are of great concern, causing huge grain yield and quality losses. Phosphorus (P) deficiency is important among the abiotic factors because most Brazilian soils have a highly P-fixing nature. Thus, large amounts of phosphate fertilizers are regularly applied to overcome the rapid precipitation of P. Searching for alternatives to improve the use of P by crops is essential to reduce the demand for P input. The use of multifunctional rhizobacteria can be considered one of these alternatives. In this sense, the objective of the present work was to select and validate bacterial strains with triple action (plant growth promoter, phosphate solubilizer, and biocontrol agent) in maize and soybean, aiming to develop a multifunctional microbial inoculant for Brazilian agriculture. Bacterial strains with high indole acetic acid (IAA) production, phosphate solubilization, and antifungal activity against soil pathogenic fungi (Rhizoctonia solani, Macrophomina phaseolina, and Fusarium solani) were selected from the maize rhizosphere. Then, they were evaluated as growth promoters in maize under greenhouse conditions. Based on this study, strain 03 (Ag75) was selected due to its high potential for increasing biomass (root and shoot) and shoot P content in maize. This strain was identified through genomic sequencing as Bacillus velezensis. In field experiments, the inoculation of this bacterium increased maize and soybean yields by 17.8 and 26.5%, respectively, compared to the control (25 kg P2O5). In addition, the inoculation results did not differ from the control with 84 kg P2O5, indicating that it is possible to reduce the application of phosphate in these crops. Thus, the Ag75 strain has great potential for developing a multifunctional microbial inoculant that combines the ability to solubilize phosphate, promote plant growth, and be a biocontrol agent for several phytopathogenic fungi.

Selective C2 electrochemical synthesis from methane on modified alumina supporting single atom catalysts

The production of C2 compounds in an aqueous solution by efficient and selective electro-conversion of methane is a challenge and of great significance topic. Here, enhanced catalysts, with tunable electrocatalytic activities with time, for direct and selective oxidation of methane to C2 products (i.e., acetic acid and ethanol) at ambient temperature were prepared by exploiting Rh and Cu single atoms dispersed on NH4BF4 modified Al2O3 nanoparticles exhibiting a large amount of Brønsted acid sites. Brønsted acid sites play a pivotal role in the final formation allowing the direct CO insertion into reaction intermediates. A high acetic acid production, over the Rh-based electrocatalyst, of 33.57 μmol/hcm2 after only 40 min of reaction was obtained. On the other hand, a selective ethanol production rate of 37.14 μmol/hcm2 after 120 min of reaction was achieved over the Cu-based catalyst, thanks to the tendency vs acetyl species formation over copper single atoms. Catalysts activity was kept stable for at least 120 min, at 2 V, and ambient temperature. The comparative analysis with the literature results highlights the high efficiency of our catalysts in selectively promoting acetic acid and ethanol productions with high yields, and stability. A novel way, exploiting single-atoms dispersed on suitable supports, for the production of performing surfaces, was provided.

Effect of Various Strains of Lactobacillus buchneri on the Fermentation Quality and Aerobic Stability of Corn Silage

The aerobic deterioration of silage nutrients is inevitable in tropical countries, causing negative consequences in animal production systems. Aiming to minimize the losses, the effects of Lactobacillus buchneri strains on fermentation profile and aerobic stability of corn silages were evaluated. The experiment was conducted under a completely randomized design with 13 treatments and three replicates. The treatments were noninoculated, commercial L. buchneri (CI), and 11 wild strains of L. buchneri: LB-56.1, LB-56.2, LB-56.4, LB-56.7, LB-56.8, LB-56.9, LB-56.21, LB-56.22, LB-56.25, LB-56.26, and LB-56.27. The treatments could be divided into three different groups according to silage pH and acetic acid concentration. Silages inoculated with LB-56.1, LB-56.4, and LB-56.9 presented higher pH, whereas intermediate values were observed for LB-56.2, LB-56.7, and LB-56.8. The highest acetic acid production was observed for LB-56.1 and LB-56.7. On the other hand, lowest concentrations were found for CI, LB-56.22, LB-56.25, LB-56.26, and LB-56.27. Higher amounts of NH3–N were observed for LB-56.8, LB-56.21, LB-56.22, and LB-56.27 silages than others. Silage inoculation with CI, LB-56.1, LB-56.2, LB-56.4, LB-56.8, LB-56.9, and LB-56.25 strains had higher aerobic stability than others (59.7 vs. 41.2 h). The L. buchneri strains LB-56.1, LB-56.2, LB-56.4, LB-56.8, LB-56.9, and LB-56.25 provided potential features to improve the aerobic stability of corn silage.

The fermentation quality of complete feed with FJLB silage additive from tropical grass

Climate change occurs because of the greenhouse gas effect. Methane from livestock accounts for 44% of methane emissions in the air, which comes from fermentation from the rumen and from feces. Many attempts have been made to reduce methane production in the rumen, including feed management. This study aims to improve the quality of complete feed fermentation with the addition of different grass source of FJLB (fermented juice of epiphytic lactic acid bacteria). The treatments consisted of T0 (Control, without FJLB), T2 (FJLB from Napier grass), T3 (FJLB from King grass). Complete feed consists of rice straw, rice bran, soybean meal, pollard and corn. The pH value of the silage with the addition of FJLB was lower than that of the silage without the addition of FJLB. The highest acetic acid production was at T3, 8.76 ppm. Meanwhile, the number of lactic acid bacteria was 5.4; 6.3 and 7.6 CFU/ml, for T0, T1 and T2, respectively. Meanwhile, ammonia production was not significantly different. The conclusion of this study is the addition of FJLB from napier grass and king improves the quality of fermentation compared to without the addition of FJLB. Good fermentation quality will improve digestibility in the rumen and is expected to reduce methane production, which is one of the greenhouse gases that causes climate change.

Biosorption efficiency of nickel by various endophytic bacterial strains for removal of nickel from electroplating industry effluents: an operational study.

Realising the hazardous effect of nickel on human health, microbes and plants are effectively used for bioremediation. The endophytic microorganisms have an important role in the phytoremediation of nickel using Vigna radiata. Therefore, in order to harness the potential of microbial strains, the present study was designed to examine the metal biosorption ability of endophytic bacterial strains isolated from plants growing in nickel-contaminated soil. A total of six endophytic nickel resistance bacteria were isolated from the plant Vigna radiata. The metal tolerant bacterial strains were identified following 16 S rRNA gene sequence analysis. Nickel biosorption estimation and plant growth-promoting (PGP) activities of isolated strains were performed and found high nickel biosorption efficiency of 91.3 ± 0.72% at 600 mg L-1 using Bacillus safensis an isolated endophytic strain from Vigna radiata. Furthermore, high indole acetic acid (IAA) and exopolysaccharide (EPS) production were obtained in all the strains as compared to without nickel-containing medium used as control. Moreover, the production of high EPS suggests improved biosorption ability of isolated endophytic strains. In addition, a kinetic study was also performed to evaluate different adsorptions isotherms and support the nickel biosorption ability of endophytic strains. The treatment of nickel electroplating industrial effluent was also demonstrated by isolated endophytic strains. Among six (6) strains, B. cereus showed maximum 57.2 ± 0.62% biosorption efficiency of nickel which resulted in the removal of 1003.50 ± 0.90 mg L-1 of nickel from the electroplating industry effluents containing initial 1791 ± 0.90 mg L-1 of nickel. All other strains were also capable of significant nickel biosorption from electroplating industry effluents as well. Thus, isolated endophytic nickel tolerant strains can be further used at large-scale biosorption of nickel from electroplating industry effluent.

Safety and efficacy of a feed additive consisting of acetic acid for all animal species.

In 2012, the EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) issued an opinion on the safety and efficacy of acetic acid when used as a technological additive (preservative) for all animal species. The characterisation and condition of use of the additive are the same as those already assessed by the FEEDAP Panel in the previous opinion on acetic acid. Acetic acid produced with the new manufacturing process complies with the specifications set by Commission Regulation (EU) No 231/2012. The FEEDAP Panel considers that the conclusions reached in the previous assessment apply to the acetic acid produced by the new manufacturing process. The FEEDAP Panel concluded that the additive is considered safe for poultry, pigs and pet animals at a maximum concentration of 2.5 g acetic acid/kg complete feed (or 1 g/L water for drinking). The known high endogenous production of acetic acid in the ruminants shows that the tolerance of these target animals is considerably higher. No data is available for salmonids. The use of the additive in animal nutrition is of no concern for consumer safety. The risks for users handling the additive depend on the concentration and include skin, eyes, and respiratory tract irritation (10–25% solution) and corrosion (> 25% solution). The use of the additive as a feed additive is considered safe for the environment. The Panel concluded that the additive has a potential to be efficacious as preservative in feedingstuffs and water for drinking. The FEEDAP Panel has some reservations about the effectiveness of acetic acid as preservative in dry feedingstuffs with a typical moisture content of ≤ 12%.

Pectic hydrolysates in the diet of Nile tilapia ( Oreochromis niloticus ): Performance, nutritional composition, histological parameters, enzymatic activity, hepatic parameters and intestinal contents

The objective of the work was to investigate the prebiotic potential of pectic hydrolysates extracted from apple pomace and passion fruit peel, added to the diet of Nile tilapia (Oreochromis niloticus). The biological assay introducing pectic hydrolysates in the diet of Nile tilapia (3.9 ± 0.67 g) lasted 42 days. Five experimental diets were evaluated, one of them a control diet and the others with the addition of pectic hydrolysates (2.5 and 5 g/kg). The fish were fed three times a day until apparent satiation. At the experimental end point, the animals were fasted for 18 h and then subjected to biometrics for data collection, tissues and digests for further analysis. The results were subjected to a normality test, followed by analysis of variance, and the means of the treatments were compared by analysing orthogonal contrasts (p < 0.05). The pectic hydrolysates did not significantly influence the performance parameters. The fish had higher body crude protein content and protein deposition with diet control than in diet 2.5 g/kg of passion fruit peel. Fat content and fat deposition were lower in 2.5 and 5 g/kg of passion fruit peel when compared to the control group. The fish feeding with 5 g/kg of apple pomace hydrolysates showed greater trypsin and chymotrypsin activity, elevation of glucose concentrations in the liver and higher acetic acid production. However, further studies should be carried out to define the adequate amounts of pectic prebiotic supplementation, aiming at analysing the effects on Nile tilapia growth and alimentary efficiency, as well as to elucidate their mechanisms of action.

The microbiome and metabolome of Napier grass silages prepared with screened lactic acid bacteria during ensiling and aerobic exposure

A full understanding of changes of the microbiome and metabolome during Napier grass silage in relation to aerobic exposure can improve the nutritional value and extend the aerobic stability of this important feed in tropical and subtropical regions. The round bale silage of Napier grass was prepared with deionized water (control) and screened strains Lactobacillus rhamnosus LR753 (LR753) and L. buchneri 40788 (LB). Silages were stored at ambient temperature (30−40 °C) for 60 days, followed by 2 and 4 days of aerobic exposure. Strains LB and LR753 significantly improved aerobic stability (>84 h vs. 18 h of control) of baled Napier grass silage by inhibiting the growth of Saccharomycetales as for the higher production of acetic acid (P < 0.05). Weissella and Issatchenkia spp. were the dominant bacteria and fungi in 60-day silage, respectively. LC–MS/MS detected a total of 426 metabolites throughout ensiling and aerobic exposure. With the decrease of Weissella spp. and the increase of Acetobacter spp., the metabolites associated with both were mainly odor-related (3-methylbutanoic acid, isoquinoline, and cuminaldehyde) and amines (tryptamine and tyramine) in control silage, while more antimicrobial activity metabolites were found in strains LB and LR753-treated silage (methylbutanoic acid, 1,2-propanediol, and tiglic acid). Screened local strain LR753 showed a promising potential for improving silage fermentation and aerobic stability of Napier grass. The present study indicates that adequately describing the microbiome and metabolome of silages during fermentation and aerobic exposure can improve ensiling practices and the screening of silage inoculants that act synergistically with the natural microbiome of the forage in hot and humid areas.

Bioremediation potential of new cadmium, chromium, and nickel-resistant bacteria isolated from tropical agricultural soil

Soil management using fertilizers can modify soil chemical, biochemical and biological properties, including the concentration of trace-elements as cadmium (Cd), chromium (Cd) and nickel (Ni). Bacterial isolates from Cd, Cr, and Ni-contaminated soil were evaluated for some characteristics for their use in bioremediation. Isolates (592) were obtained from soil samples (19) of three areas used in three maize cultivation systems: no-tillage and conventional tillage with the application of mineral fertilizers; minimum tillage with the application of sewage sludge. Four isolates were resistant to Cr3+ (3.06 mmol dm−3) and Cd2+ (2.92 mmol dm−3). One isolate was resistant to the three metals at 0.95 mmol dm−3. All isolates developed in a medium of Cd2+, Cr3+ and Ni2+ at 0.5 mmol dm−3, and removed Cd2+ (17–33%) and Cr6+ (60–70%). They were identified by sequencing of the gene 16S rRNA, as bacteria of the genera Paenibacillus, Burkholderia, Ensifer, and two Cupriavidus. One of the Cupriavidus isolate was able to remove 60% of Cr6+ from the culture medium and showed high indole acetic acid production capacity. We evaluated it in a microbe-plant system that could potentially be deployed in bioremediation by removing toxic metals from contaminated soil.

Contribution of autochthonous yeasts with probiotic potential to the aroma profile of fermented Guajillo pepper sauce.

Three yeast strains with probiotic potential, Hanseniaspora opuntiae, Pichia kudriavzevii, and Wickerhamomyces anomalus were inoculated in the fermentation of Guajillo chilli pepper (Capsicum annuum L.) sauce, and the different aroma profiles were investigated. Using headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) analysis and gas chromatography-olfactometry (GCO), flavour compound production was evaluated during the fermentation of the Guajillo chilli pepper sauces. A total of 78 volatile compounds were identified during the yeast fermentation of the sauce. Most aldehydes and terpenes detected were present at the beginning of the fermentation, indicating a Guajillo chilli pepper origin. Among the 34 active aroma compounds detected by GCO, propanoic acid (cheesy), 3-methylbutanoic acid (sharp, cheese), ethyl 2-methylbutanoate (fruity), and 6-methyl-5-hepten-2-one (strong, citrus) were identified as key aroma contributors produced by the inoculation of the yeasts. A different aroma profile was produced by probiotic yeast. Hanseniaspora opuntiae produced an aroma profile with herbal and green notes based on high production of aldehydes, ketones, and acetic acid. Pichia kudriavzevii and W. anomalus produced fruity, green-herbal, and cheesy notes based on ester compounds, alcohol and branched-chain acids production although, the production of propanoic acid by W. anomalus increased the cheesy character in the sauces. The aroma profile of fermented chilli pepper sauces depends not only on the chili pepper varieties used but also on the fermentation process as a source of aroma compounds. The use of probiotic yeast can be used to improve and diversify the aroma profile of fermented chilli pepper sauces. © 2020 Society of Chemical Industry.

Bioaugmentation with Enterococcus casseliflavus: A Hydrogen-Producing Strain Isolated from Citrus Peel Waste

To isolate, identify and characterize an anaerobic strain from in natura CPW, in relation to the consumption of different carbon sources, growth kinetics and H2 production after bioaugmentation. Several substrates were evaluated (glucose, fructose, sucrose, xylose, starch, cellobiose, cellulose and lactose), and its optimal concentration was evaluated by Experimental Design method, besides the application of the isolated strain in citrus peel waste (CPW). A facultative anaerobic strain, similar (99%) to Enterococcus casseliflavus, was isolated from in natura citrus pulp and bagasse. Xylose was the monomer from which there was greater H2 production (10.3 mmol L−1). For 0.5 to 6.5 gxylose L−1, 3.0 to 12.9 mmol H2 L−1 was obtained, respectively. Generation time (Tg) of 0.35 h and specific growth (µ) of 1.98 h−1 for pH 7.0, 37 °C and 2 g glucose L−1 was obtained for E. casseliflavus. In bioaugmentation assays (CPW + E. casseliflavus), highest maximum H2 production potential (P = 13.9 mmol L−1), maximum H2 production rate (Rm = 1.09 mmol h−1) and time to start the H2 production (λ = 2.12 h−1) was observed when compared to glucose (P = 9.1 mmol L−1; Rm = 1.99 mmol h−1; λ = 4.08 h−1). From glucose, there was prevalence of butyric acid pathway (759 mg L−1) in relation to acetic acid (303 mg L−1). From CPW, there was higher production of acetic acid (878 mg L−1) in relation to butyric (147 mg L−1). The application of E. casseliflavus by bioaugmentation is an alternative for biodigestion of complex substrates, such as CPW, to obtain products of biotechnological interest.

Enhanced fermentative hydrogen production from industrial wastewater using mixed culture bacteria incorporated with iron, nickel, and zinc-based nanoparticles

The present study assessed the efficiency of utilizing mixed culture bacteria (MCB) incorporated with individual nanoparticles (NPs), i.e., hematite (α-Fe2O3), nickel oxide (NiO), and zinc oxide (ZnO), dual NPs (α-Fe2O3 + NiO, α-Fe2O3 + ZnO, and NiO + ZnO), and multi-NPs (α-Fe2O3 + NiO + ZnO) for hydrogen production (HP) from industrial wastewater containing mono-ethylene glycol (MEG). When MCB was individually supplemented with α-Fe2O3 (200 mg/L), NiO (20 mg/L), and ZnO NPs (10 mg/L), HP improved significantly by 41, 30, and 29%, respectively. Further, key enzymes associated with MEG metabolism, such as alcohol dehydrogenase (ADH), aldehyde dehydrogenase (ALDH), and hydrogenase (hyd), were rapidly and substantially enhanced in the medium. NiO and ZnO NPs notably promoted ADH and ALDH activities, respectively, while α-Fe2O3 exhibited superior impact on hyd activity. Maximum hydrogen production rate was concomitant with higher acetic acid production and lower residual acetaldehyde and ethanol. HP using MCB supplemented with individual NiO (20 mg/L) and ZnO NPs (10 mg/L) further improved by 8.0%–14% when dual and multi-NPs were used; the highest HP was recorded when multi-NPs were used. In addition, NPs incorporation resulted in substantial increase in the relative abundance of Clostridiales (belonging to family Clostridiaceae; > 83%). Overall, this study provides significant insights into the impact of NPs on hydrogen production from MEG-contaminated wastewater.