This research shows the effect of dilute acid pretreatment with various sulfuric acid concentrations (0.5–2.0% wt/vol) on enzymatic saccharification and fermentation yield of rye straw. After ...pretreatment, solids of rye straw were suspended in Na citrate buffer or post‐pretreatment liquids (prehydrolysates) containing sugars liberated after hemicellulose hydrolysis. Saccharification was conducted using enzymes dosage of 15 or 25 FPU/g cellulose. Cellulose saccharification rate after rye straw pretreatment was enhanced by performing enzymatic hydrolysis in sodium citrate buffer in comparison with hemicellulose prehydrolysate. The maximum cellulose saccharification rate (69%) was reached in sodium citrate buffer (biomass pretreated with 2.0% wt/vol H2SO4). Lignocellulosic complex of rye straw after pretreatment was subjected to separate hydrolysis and fermentation (SHF) or separate hydrolysis and co‐fermentation (SHCF). The SHF processes conducted in the sodium citrate buffer using monoculture of Saccharomyces cerevisiae (Ethanol Red) were more efficient compared to hemicellulose prehydrolysate in respect with ethanol yields. Maximum fermentation efficiency of SHF processes obtained after rye straw pretreatment at 1.5% wt/vol H2SO4 and saccharification using enzymes dosage of 25 FPU/g in sodium citrate buffer, achieving 40.6% of theoretical yield. However, SHCF process using cocultures of pentose‐fermenting yeast, after pretreatment of raw material at 1.5% wt/vol H2SO4 and hydrolysis using enzymes dosage of 25 FPU/g, resulted in the highest ethanol yield among studied methods, achieving 9.4 g/L of ethanol, corresponding to 55% of theoretical yield.
Volatile sulfur compounds (VSCs) play an important role in the aroma profile of fermented beverages. However, because of their low concentration in samples, their analysis is difficult. The headspace ...solid-phase microextraction (HS-SPME) technique coupled with gas chromatography and mass spectrometry (GC-MS) is one of the methods successfully used to identify VSCs in wine and beer samples. However, this method encounters more obstacles when spirit beverages are analyzed, as the ethanol content of the matrix decreases the method sensitivity. In this work, different conditions applied during HS-SPME/GC-MS analysis, namely: ethanol concentration, salt addition, time and temperature of extraction, as well as fiber coating, were evaluated in regard to 19 sulfur compounds. The best results were obtained when 50/30 μm Divinylbenzene/Carboxen/Polydimethylsiloxane (DVB/CAR/PDMS) was used to preconcentrate the analytes from the sample at 35 °C for 30 min. The dilution of samples to 2.5%
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ethanol and the addition of 20%
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NaCl along with 1% EDTA significantly improves the sensitivity of extraction. The optimized method was applied to three fruit brandy samples (plum, pear, and apple) and quantification of VSCs was performed. A total of 10 compounds were identified in brandy samples and their concentration varied greatly depending on the raw material used from production. The highest concentration of identified VSCs was found in apple brandy (82 µg/L).
The study describes sulfuric acid pretreatment of straw from
L. (rye straw) to evaluate the effect of acid concentration and treatment time on the efficiency of biofuel production. The highest ...ethanol yield occurred after the enzyme treatment at a dose of 15 filter paper unit (FPU) per gram of rye straw (subjected to chemical hydrolysis with 2% sulfuric acid (SA) at 121 °C for 1 h) during 120 h. Anaerobic digestion of rye straw treated with 10% SA at 121 °C during 1 h allowed to obtain 347.42 L methane/kg volatile solids (VS). Most hydrogen was released during dark fermentation of rye straw after pretreatment of 2% SA, 121 °C, 1 h and 1% SA, 121 °C, 2 h-131.99 and 134.71 L hydrogen/kg VS, respectively. If the rye straw produced in the European Union were processed into methane, hydrogen, ethanol, the annual electricity production in 2018 could reach 9.87 TWh (terawatt-hours), 1.16 TWh, and 0.60 TWh, respectively.
Throughout history, the fermentation of fruit juices has served as a preservation method and has enhanced the retention of bioactive constituents crucial for human well-being. This study examined the ...possibility of orange and black currant juice fermentation with the probiotic yeast Saccharomyces cerevisiae var. boulardii. Saccharomyces bayanus was used as the reference. The ethanol concentration of the orange juices fermented without added glucose was close to 27 g/L. Adding glucose to the juice increased the alcohol produced by up to 65.58 ± 1.84 g/L (for the orange juice). For the same wort fermented by S. bayanus, the final ethanol concentration was 71.23 ± 1.62 g/L. Regardless of the type of yeast and additives used, the samples retained much of the color of the unfermented juice. The polyphenols content in the fermented samples was close to the initial polyphenols content in the juices. The sensory attributes of the juices fermented by the probiotic yeast did not differ from the samples fermented by S. bayanus. Fermenting fruit juices with probiotic yeasts offers a commercially viable and sensorially appealing method to enhance the product’s value by imparting it with probiotic properties.
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•Inoculum/substrate preconditioning stimulates power production in microbial fuel cell.•For the first time bacterial and fungal species were identified in anode ...biofilm.•Fungi-bacteria consortium enables power production from wood industry wastewater.
Production of electricity from wastewater in microbial fuel cells is possible due to the cooperation of hydrolytic, fermentative, and electrogenic microorganisms coexisting in a consortium. In this article, we present results that indicate that we can stimulate electrical current production from wastewater, from which power could not be produced without influencing the growth of a microbial consortium through preconditioning. The wood industry wastewater was thermally preconditioned at 45 °C before introducing it to microbial fuel cells which resulted in changing microbial consortium composition by the development of new species. In the anodes of microbial fuel cells that were fed preconditioned wastewater, we identified, by the means of metagenomic analysis, mixed fungi-bacteria syntrophic consortium that was capable of producing electricity from wood industry wastewater. The developed syntrophic consortium was dominated by fungi of the Trichocomaceae sp. and two bacteria species: Achromobacter insolitus and Geobacter sulfurreducens. None of these species were present in raw wastewater. Power was not generated in microbial fuel cells that were fed raw wastewater, but wastewater preconditioning stimulated power production at 0.33 W/m2 what responded to 1 A/m2 current density. The developed consortium decomposed cellulose present in wastewater into glucose and fermented it into acids and alcohols. We showed that stimulation of power production may be driven through substrate preconditioning before it is used in microbial fuel cells. By selecting growth conditions for a consortium, we may regulate its microbial composition and facilitate production of an electrical current from substrates that could not previously be used in microbial fuel cells.
This paper evaluated the effectiveness of nitric acid pretreatment on the hydrolysis and subsequent fermentation of Jerusalem artichoke stalks (JAS). Jerusalem artichoke is considered a potential ...candidate for producing bioethanol due to its low soil and climate requirements, and high biomass yield. However, its stalks have a complexed lignocellulosic structure, so appropriate pretreatment is necessary prior to enzymatic hydrolysis, to enhance the amount of sugar that can be obtained. Nitric acid is a promising catalyst for the pretreatment of lignocellulosic biomass due to the high efficiency with which it removes hemicelluloses. Nitric acid was found to be the most effective catalyst of JAS biomass. A higher concentration of glucose and ethanol was achieved after hydrolysis and fermentation of 5% (w/v) HNO3-pretreated JAS, leading to 38.5 g/L of glucose after saccharification, which corresponds to 89% of theoretical enzymatic hydrolysis yield, and 9.5 g/L of ethanol. However, after fermentation there was still a significant amount of glucose in the medium. In comparison to more commonly used acids (H2SO4 and HCl) and alkalis (NaOH and KOH), glucose yield (% of theoretical yield) was approximately 47–74% higher with HNO3. The fermentation of 5% nitric-acid pretreated hydrolysates with the absence of solid residues, led to an increase in ethanol yield by almost 30%, reaching 77–82% of theoretical yield.
Despite the significant progress in the research, the problem of finding an efficient method for producing bioethanol from renewable lignocellulosic waste materials remains unresolved. Our ...investigation aimed to assess the efficacy of ethanol production from sugar beet pulp (SBP) utilising various approaches, including pretreatment variations, enzymatic processes, and microbial hydrolysis. Our research involved using the post-cultivation concentrate of T. viride LOCK 0588 grown in the SBP-based medium as a source of enzymes. The SBP hydrolysis process was carried out for 48 h at 50 °C. The quantity of sugar released, up to 61 g dm−3, through the utilisation of this extract proved to be on par with the outcomes achieved by the application of the commercial Cellic Ctec2 preparation. The final yields of the ethanol production with the use of the coculture of S. cerevisiae (Ethanol Red) and Scheffersomyces stipitis LOCK 0047 strain were in the range 5.1 ± 0.11 kg 100 kg−1 ÷ 5.38 ± 0.11 kg 100 kg−1. These results provide a solid basis for improving larger-scale industrial procedures that involve converting SBP into bioethanol using a cost-efficient approach of microbial hydrolysis with T. viride and a blend of pentose and hexose fermenting yeast.
This study set out to assess the acetone content in rye sweet mashes prepared using the thermal-pressure method of starch liberation, and to investigate the formation of 2-propanol during the ...fermentation process. In the first set of experiments, we evaluated the correlation between the color and the content of acetone and furfural in industrially produced sweet mashes (
= 37). The L * value was negatively correlated with the content of both acetone and furfural, while chromatic parameters a * and b * and the yellowness index (YI) had strong positive correlations with acetone (r > 0.9) and furfural (r > 0.8 for a * and r > 0.9 for b * and YI). In the second set of experiments, we assessed the concentration of acetone and 2-propanol in distillery rye mashes, fermented by
yeast and lactic acid bacteria. The influence of fermentation temperature on the formation of 2-propanol was also evaluated. The presence of 2-propanol in the post-fermentation media was confirmed, while a decrease in acetone content was observed. Fermentation temperature (27 °C or 35 °C) was found to have a significant effect on the concentration of 2-propanol in trials inoculated with lactic bacteria. The content of 2-propanol was more than 11 times higher in trials fermented at the higher temperature. In the case of yeast-fermented mashes, the temperature did not affect 2-propanol content. The acetone in the sweet mash was assumed to be a precursor of 2-propanol, which was found in the fermented mashes.
High concentrations of aldehydes may result in poor-quality agricultural distillate. We investigate the influence of the method of mash preparation, the initial pH of the mashes, and different yeast ...strains on the fermentation efficiency and concentration of aldehydes from C2 (acetaldehyde) to C7 (enanthaldehyde) in rye mashes. The tested factors were revealed to have a differentiated influence on both the process efficiency and the concentrations of aldehydes, especially in the case of the dominant acetaldehyde. Mashes obtained from steamed rye grain showed significantly higher fermentation efficiencies than those prepared by the pressureless method. Increasing the pH of the sweet mashes from 4.5 to 6.0 resulted in significantly higher concentrations of acetaldehyde, especially in the case of steamed rye grain. Moreover, an increase in the concentrations of other aldehydes, i.e., from C3 (propionaldehyde) to C5 (valer- and isovaleraldehyde) was observed. A high fermentation efficiency and the lowest acetaldehyde concentrations were obtained from steamed rye mashes with an initial pH of 4.5, fermented using the yeast strains DistilaMax GW and DistilaMax HT. DistilaMax HT yeast also provided a relatively low concentration of acetaldehyde in mashes with an initial pH in the range of 4.5–5.5 prepared by the energy-saving pressureless method.
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