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•The highest total VFAs concentration at RT=5days was achieved at acidic environment.•Alkaline environment was favorable at long RT due to WAS disintegration.•Acetate dominated all of ...the VFAs most likely due to WAS disintegration.•Caproate concentration doubled with prolonging RT from 5 to 15days.
Mixed culture fermentation consists of stable microbial population hence waste could be potentially used as a substrates. The aim of the work was to investigate the impact of pH and retention time on the anaerobic mixed culture fermentation. Trials at different pH (4–12) in unbuffered systems were conducted for 5, 10 and 15days. The highest VFAs concentration was achieved after 15days at pH 10 (0.62g/gVSadded), promising results were also achieved for pH 11 (0.54g/gVSadded). For pH 4 and short retention time propionic acid was the major product instead of acetic acid. For batches run at 15days (besides pH 6) caproic acid presence was noticed whereas at pH 11 occurrence of succinic was quantified. Significant correlation between operational factors and fermentation’s effluents was proved. Throughout changing simple operating parameters one could design process to produce desirable concentration and composition of VFAs.
•Different substrates will lead to a similar spectrum of products in the MCF process.•In the acidic pH there is higher diversity of volatile fatty acids.•Pre-adjusted alkaline pH is favorable for ...hydrolysis of complex organic matter.
Volatile fatty acids (VFAs) are obtained during chemical routes from non-renewable petrochemicals. Intensive exploitation of oil resources have renewed the idea of VFAs production during biological routes, mainly throughout anaerobic mixed culture fermentation (MCF). We carried out MCF trials at initial acidic (5.0), neutral (7.0, with addition of specific methanogenesis inhibitor) and alkaline (11.0) pH conditions for four different substrates i.e. maize silage, cheese whey, microalgae biomass and glucose. The goal of the study was to investigate the impact of the substrate complexity on the produced VFAs’ quality and quantity. The highest VFAs concentration occurred in neutral pH proceeded by initial alkaline pH (0.83gVFAs/gSCOD for microalgae biomass, 0.78gVFAs/gSCOD for maize silage and 0.71gVFAs/gSCOD for cheese whey, respectively). In the fermentation of glucose, the highest VFAs concentration was achieved in neutral pH. We demonstrated that the alkaline pH was favorable for hydrolysis of complex organic matter (acidification yield over 71% for maize silage fermentation), while the neutral pH was beneficial for the acidogenesis and the overall VFAs production. Our findings showed that it was possible to carry out efficient and stable MCF process without using a large amounts of acid or base for pH adjustment and that the distribution of VFAs only merely depended on the substrate type.
In light of an increasing demand for energy and sustainable development, bioenergy production is a must. A carboxylate platform-based bioprocess now enables the conversion of organic waste into a ...valuable bioproduct via open culture fermentation due to a complex microbial activity. Caproic acid is one of the promising products that can be further processed into liquid biofuels. In this study we have shown stable, long-term production of n -caproate from acid whey by shaping the reactor microbiome in a UASB bioreactor. The reactor was operated at pH 5.5 with gradually decreasing hydraulic retention time. The results showed acceleration of n -caproate formation and the highest average n -caproate production rate that lasted for 37 days was 134.3 ± 30.9 mmolC L −1 d −1 (0.11 g L −1 h −1 ) (with a median of 146.1 mmolC L −1 d −1 ) and specificity between 58 and 83% (with a median of 79%). Microbiological studies showed the prevalence of fermentative microorganisms from the families Coriobacteriaceae, Ruminococcaceae and Prevotellaceae that are the likely agents for lactose and lactate to n -caproate conversion. A flow cytometry based evaluation of the reactor microbiome demonstrated the inherent heterogeneity of microbial subpopulations in terms of microbial activity at different points of fermentation.
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•Decreasing the HRT to achieve high OLR reduces the hydrolysis yield.•Shortening of HRT resulted in decreasing of TVFAs produced from cheese whey.•Changes in HRT and OLR did not ...affect production of TVFAs from sludge.•TVFAs composition was impacted by substrate type and microbial biodiversity.•Microbial community from substrate tended to dominate bioreactor.
The objectives of this study were to investigate the effect of hydraulic retention time (HRT) and organic loading rate (OLR) on the volatile fatty acids (VFAs) production from cheese whey and sludge, and to find the relation between total volatile fatty acids (TVFAs) accumulation at different HRT and OLR and the corresponding bacterial community. The highest concentrations of butyrate (5.0 g COD/L), valerate (3.8 g COD/L), caproate (4.2 g COD/L) and heptate (0.8 g COD/L) were obtained from whey fermentation, where proportion of acetate increased with HRT shortening (from 8.3% to 83.5% for HRT of 20 to 1 day, respectively). The highest concentrations of acetate (1.6 g COD/L), propionate (2.9 g COD/L), iso-butyrate (0.8 g COD/L) and iso-valerate (1.8 g COD/L) were obtained from sludge fermentation, where proportion of acids was independent of HRT. Bacterial communities consisted mostly of the phyla Firmicutes, Cloacimonetes, Proteobacteria and uncultured bacterium clones. The bacterial community originating from the substrate was able to adapt to the applied bioreactor conditions and it had an immense impact on the process performance.
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•Increase in carboxylates concentration was accompanied by a decline in lactate.•Lactate with ethanol promote lactate oxidation coupled to chain elongation.•Lactic acid strongly ...affects the chain elongation.•Ionic liquid are promising for liquid-liquid extraction of carboxylates.•It is possible to economically effective produce caproic acid.
The objective of this study was to investigate the potential of supplementing ethanol and lactic acid as electron donors in reverse β-oxidation for short chain carboxylic acids chain elongation during anaerobic fermentation of acid whey. Best results were achieved when lactic acid was added at concentration of 300 mM. It resulted in medium chain carboxylic acids (MCCAs) concentration of 5.0 g/L. In the trials with ethanol addition, the overall yield was 20% lower. Subsequently liquid-liquid extraction with ionic liquids (ILs) was investigated as a potential purification method of caproic acid. The most promising, with respect to recovery of caproic acid, was piperazinium IL C1C1C10PpzNTF2, however, the selectivity was only 0.39. Less effective C1C1C6PpzNTF2 recovered 85.9% of caproic acid while reaching a higher selectivity of 0.53. Technoeconomic model revealed that to meet the conservative value of $2.25 per kg of caproic acid, the downstream processing should not exceed $0.65 per kg.
The objective of this study was to investigate the effect of substrate composition on chain elongation pathways and on shaping reactor microbiome during open culture fermentation (OCF). The process ...was performed in a continuous mode in an upflow anaerobic sludge blanket (UASB) reactor fed with either fresh acid whey (AW) or AW at controlled stage of prefermentation (with controlled content of electron donors). Dosing AW with an increasing ethanol loading rate led to ethanol oxidation and short chain carboxylic acids (SCCAs) generation. Change of the feedstock composition (higher lactate and lactose content and ethanol cut off) shifted the process outcome towards medium chain carboxylic acids (MCCAs) production, with caproate as the main product. The MCCAs production rate has grown from 0.7 ± 0 to 4.12 ± 1 g/L/day (38.3 ± 5 to 212.6 ± 60 mmol C/L/day) and reached specificity of 48 ± 18% mol C. The differentiation between microbiome samples confirmed the reactor microbiome shaped according to the feed composition. The only known caproic acid producers were represented by Caproiciproducens ssp., that reached a relative OTU abundance between 3 and 7%. The developed method enables to substitute the use of fossil resources with products from the OCF of waste and wastewater. Thus, it contributes to reduce the carbon footprint and enhance the sustainability of the chemical industry.
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•The feed composition strongly influenced the chain elongation process.•Low ethanol content and abundant lactate were essential to produce caproate.•Overdosing with ethanol directed the process towards ethanol oxidation.•Removal of ethanol resulted in sharp SCCAs drop and growth of MCCAs production.•Maximum caproate production rate reached 4.1 g/L/day at HRT of 1.25 day.
Open culture fermentation (OCF) is a promising technology for converting different organic waste into carboxylic acids (CAs) and alcohols in the context of biorefinery. This study investigated OCF to ...enhance the production of CAs and alcohols from three different monosaccharides: glucose, xylose, galactose and a mixture of two sugars: glucose with galactose. In addition, more complex substrates, such as maize silage and strawberry wastewater were used as well. The investigated variables included following operational parameters: substrate type, pH, retention time and sugar loading. Promising results were obtained for complex substrates. The highest CAs yield was noticed for raw maize silage at pH 8 and RT 1 day. For monosaccharides the most efficient process was the co-fermentation (glucose/galactose) (substrate loading 4 g L−1). CAs composition varied with the changing pH and type of sugar and substrate: in neutral conditions, acetic acid; in acidic conditions, acetic and butyric acids; and in alkaline conditions butyric acid were dominant, respectively. Statistical inference showed optimal conditions for the production of defined compounds from a specific monosaccharide, which could be helpful for designing experiments aiming at particular CA.
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•OCF is a promising technology for converting organic waste into CAs and alcohols.•High substrate loading changes the OFC course.•pH and substrate type are the most important process parameters.
In light of an increasing demand for energy and sustainable development, bioenergy production is a must. A carboxylate platform-based bioprocess now enables the conversion of organic waste into a ...valuable bioproduct
via
open culture fermentation due to a complex microbial activity. Caproic acid is one of the promising products that can be further processed into liquid biofuels. In this study we have shown stable, long-term production of
n
-caproate from acid whey by shaping the reactor microbiome in a UASB bioreactor. The reactor was operated at pH 5.5 with gradually decreasing hydraulic retention time. The results showed acceleration of
n
-caproate formation and the highest average
n
-caproate production rate that lasted for 37 days was 134.3 ± 30.9 mmolC L
−1
d
−1
(0.11 g L
−1
h
−1
) (with a median of 146.1 mmolC L
−1
d
−1
) and specificity between 58 and 83% (with a median of 79%). Microbiological studies showed the prevalence of fermentative microorganisms from the families Coriobacteriaceae, Ruminococcaceae and Prevotellaceae that are the likely agents for lactose and lactate to
n
-caproate conversion. A flow cytometry based evaluation of the reactor microbiome demonstrated the inherent heterogeneity of microbial subpopulations in terms of microbial activity at different points of fermentation.
A carboxylate platform-based bioprocess now enables the conversion of organic waste into a valuable bioproduct
via
open culture fermentation due to a complex microbial activity.
Somatic embryogenesis (SE), which is a process that involves the in vitro-induced embryogenic reprogramming of plant somatic cells, requires dynamic changes in the cell transcriptome. These changes ...are fine-tuned by many genetic and epigenetic factors, including posttranslational histone modifications such as histone acetylation. Antagonistically acting enzymes, histone acetyltransferases (HATs) and deacetylases (HDACs), which control histone acetylation in many developmental processes, are believed to control SE. However, the function of specific HAT/HDACs and the genes that are subjected to histone acetylation-mediated regulation during SE have yet to be revealed. Here, we present the global and gene-specific changes in histone acetylation in Arabidopsis explants that are undergoing SE. In the TSA (trichostatin A)-induced SE, we demonstrate that H3 and H4 acetylation might control the expression of the critical transcription factor (
) genes of a vital role in SE, including
,
(
),
(
) and
(
). Within the HATs and HDACs, which mainly positively regulate SE, we identified HDA19 as negatively affecting SE by regulating
,
and
. Finally, we provide some evidence on the role of HDA19 in the histone acetylation-mediated regulation of
during SE. Our results reveal an essential function of histone acetylation in the epigenetic mechanisms that control the
genes that play critical roles in the embryogenic reprogramming of plant somatic cells. The results implicate the complexity of Hac-related gene regulation in embryogenic induction and point to differences in the regulatory mechanisms that are involved in auxin- and TSA-induced SE.
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