Tailored production of butyric acid from mixed culture fermentation of food waste (original) (raw)
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Environmental Science and Pollution Research
This study is focused on the effects of pH on the production of volatile fatty acids (VFAs) and their distribution through the acidogenic fermentation of source-sorted organic fraction of municipal solid waste (OFMSW) from a mechanical-biological treatment (MBT) plant, and food waste (FW) from a university canteen. In semi-continuous lab-scale digesters using OFMSW at a hydraulic retention time (HRT) of 3.5 days under acidic conditions (pH 6.0), the VFA concentration in the effluent increased to 9.8-11.5 g L −1 (VS content of the feedstock between 4.2 and 5.2% w/w), while its individual VFA profiling was similar to the influent which was already prefermented (namely, C 2 35-41%, C 3 18-22%, C 4 17-21%, and C 5 9-12%). When working with the same conditions but using FW as feedstock, an effluent with a VFA concentration up to 11.5 g VFA L −1 (FW with a VS content of 5.5% w/w) and a stable distribution of C 2 and C 4 acids (up to 60.3% and 12.9%, respectively) but with very low quantities of C 3 and C 5 acids (lower than 1.8 and 2.7%, respectively) was obtained. Anaerobic batch tests using FW revealed that alkaline pH near 9 could lead to higher VFA production with high acetic acid content when compared to pH 6. In the semi-continuous fermenters working at alkaline conditions (pH 9.5-10) using OFMSW and FW, an enhanced solubilization of organic matter was registered with respect to the fermenters working under acidic conditions. This fact was not reflected in a higher VFA production when using OFMSW as feedstock, probably due to free ammonia inhibition, since OFMSW was mixed in the MBT plant with supernatant from anaerobic digestion of this biowaste. However, when using FW, alkaline conditions lead to an enhanced VFA production with respect to the reactor working under acidic conditions, being acetic acid the predominant product, which represented up to 91% of the VFA spectrum obtained.
A study of fatty acid production by Clostridium butyricum
2012
This thesis investigates the fatty acid production from carbohydrates using C. butyricum. In nature a common route for the anaerobic degradation o f carbohydrate in the environment is via methanogenesis. A t the heart o f these processes however, is the metabolism o f a diversity o f carbohydrate materials that produce a few fatty acids (acetate and butyrate) which are then slowly converted to methane. In this context, fatty acids can be considered as a common endproduct/intermediate from carbohydrate degradation that could be used to produce chemicals. Already, acetic and butyric acid are important feedstock chemicals in the pharmaceutical, food and industrial sectors and there is potential to expand this further. As a first step to investigate the conversion o f waste carbohydrate to fatty acids for chemical production, C. butyricum, a strictly anaerobic bacterium, was investigated as a model system for the potential production o f acetic and butyric acid. The production efficiency o f C. butyricum relies on the type o f substrate, production methodology, the strain and environmental conditions. Pure cultures o f C. butyricum were investigated for fatty acid production from carbohydrates. Initial studies involved medium optimization in test tube culture for high growth rate and maximum biomass production (O D raax). In this medium, glucose was selected as the main substrate together with yeast extract, K H 2P 0 4 and N H 4(S O)4. The studies were carried out in three types o f p H controlled reactors; batch stirred tank (S R T), continuously stirred tank (C S TR) and membrane bioreactor (M B R) A comparison the fatty acid production kinetics and productivity in each reactor was undertaken and the effect o f glucose concentration and where appropriate, glucose feed rates, were also investigated. The results show that fatty acid production could be carried out in all three fermentation systems. A common observation in these systems was that fatty acid production was influenced by the glucose concentration in that at low glucose concentration the ratio o f acetate to butyrate was about 30:1 while at higher concentrations the ratio was reduced to about 3:1 on a molar basis. The detailed kinetic studies generated unique data for this organism and shows that the maintenance coefficient (m s) increase with increasing glucose concentration (0.02 to 1.1 g substrate/g cell/h), due to mainly to end product inhibition and the true yield (Y^ max) was around 0.2 for all glucose concentrations tested. Meanwhile substrate saturation (K s) decreased with increasing glucose concentrations (2.06-6.41 g/L). This observation was atypical to that observed in other anaerobic fermentations by previous workers. A comparison o f fatty acid productivities using a 10g/I glucose feed in the 3 reactors for acetic acid were 0.95 g/l/h for STR, 4.41 g/l/h for C S TR and 37.88 g/l/h for M B R and for butyric acid 0.15 g/l/h for STR, 1.27 g/l/h for C S T R and 14.34 g/l/h M B R. Although, previous work in this area is limited the data obtained in this study was also compared with other published work and this suggests that the production o f fatty acid, especially acetic and butyric acid in the M B R system is by far the most productive yet reported. The results are discussed in the context o f the waste treatment process for fatty acid production and its application to waste conversion and its further development. phosphate on growth rate 4.2.3The effect o f ammonia sulphate on growth rate 4 .2.4 The effect of glucose on growth rate 4.2.5 Brief conclusion for preliminary tests 4.3 Growth experiments in batch culture with pH control 4.3.1The effect of glucose concentrations on growth rate 4.3.2 The effect of glucose concentration o f yield 4.3.3 Concentration o f acetic and butyric acid form ation 4.3.4 The relationship total acid production and initial glucose concentration 4.3.5 The percentage of glucose converted to acetic and butyric acid 4.3.6 Effect o f glucose concentration on the requirem ent for sodium hydroxide 4.3.7 Relationship between cumulative requirem ent for sodium hydroxide and fatty acid production 4.3.8. Ferm entation balances 4.4 Comparison the ferm entation of glucose, xylose and starch in the batch system by C.butyricum 4.4.1 Biomass yield 4.4.2 Growth rate and maximum biomass production 4.4.3 Fatty acid production 4.4.4 Comparison end product form ation on glucose, xylose and starch. 4.5 Conclusions 96 CHAPTER 5: CONTINUOUS CULTURE 5.1 Introduction 98 5.2 The theory o f continuous cultivation. 98 5.2.1Actual biomass yield (Yx/s max) and m aintenance coefficient (ms) 5.2.2 M axim um specific growth rate (|im ax) and substrate saturation constant (Ks) 5.2.3Theoretical calculation o f cell concentration 5 .2.4 Biomass productivity (Qx) 5.3 Effect o f dilution rate to the growth of C.butyricum 5.4 Evaluation o f kinetic and yield parameters 5.4.1M axim u m yield and maintenance coefficient 5.4.2 Substrate saturation constant 5.5 Product form ation 5.5.1Relationship betw een dilution and acetic acid production 5.5.2Relationship betw een dilution and butyric acid production 5.5.3 Relationship betw een dilution rate and carbon balance 5.5.4 Relationship betw een dilution and total acid production 5.5.5 Ratio betw een acetic and butyric acid 5.6 Conclusions CHAPTER 6: MEMBRANE BIOREACTOR 6.1 Introduction 6.2 M em b ran e bioreactor theory 6.3 The perm eate flux and trans m em brane pressure 6.3.1Effect of media on m em brane perform ance 6.4 M em b ran e bioreactor culture 6.4.1 Cell grow th and glucose consumption 6.4.2 Relationship between perm eation rates w ith grow th rate (p) 6.5 Acetate and butyrate product rate 6.5.1 Ratio betw een acetic and butyric acid 6.5.2 Relationship betw een cumulative of NaOH to cum ulative of total acid production.
Current perspectives on acidogenic fermentation to produce volatile fatty acids from waste
Reviews in Environmental Science and Bio/Technology, 2021
Volatile fatty acids (VFAs) are key platform chemicals used in a multitude of industries including chemicals, pharmaceuticals, food and agriculture. The current route for VFA production is petrochemical based. VFAs can be biologically produced using organic wastes as substrate, therefore directly contributing to a sustainable economy. This process is commonly known as acidogenic fermentation (AF). This review explores the current research on the development of AF processes optimized for VFA production. Three process steps are considered: feedstock pretreatment, fermentation, and primary product recovery with a focus on in situ recovery. Pretreatment is required for recalcitrant feedstocks, especially lignocellulosic substrates. Different pretreatment techniques for AF application have not been studied in depth. The operational parameters of AF (temperature, pH, hydraulic retention time, substrate concentration, etc.) highly influence microbial activity, VFA yields and product distri...
Waste and Biomass Valorization, 2018
Purpose The present study was aimed to develop a successful bioprocess through solid state fermentation (SSF) technique for the butyric acid production using agriculture wastes like wheat bran, rice polishings and molasses anaerobically by Clostridium tyrobutyricum DSM 2637. Methods Different physiochemical parameters like substrate: water ratio, inoculum volume, different ionic salts concentrations, an additive effect of molasses and corn steep liquor were optimized to boost the butyric acid production through SSF of the growth medium anaerobically by Clostridium tyrobutyricum DSM 2637 at 37 °C, pH 6.0. The fermentation of the growth medium was terminated after 72 h of incubation. Quantification of butyric acid was done by Deniges method. Results The growth medium containing rice polishings, molasses, and wheat bran when subjected to determine substrate: water ratio through SSF at 37 °C, pH 6.0 anaerobically by Clostridium tyrobutyricum DSM 2637 yielded 5.63, 5.5, 4.26 mg/100 g of butyric acid respectively. Conclusions The present investigation demonstrated that rice polishings supplemented with corn steep liquor is a good agricultural waste for butyric acid production. The SSF technique can efficiently and successfully be utilized for better yield of butyric acid on the pilot scale.
Bioresource technology, 2017
Recently, efficient disposal of food waste (FW) with potential resource recovery has attracted great attentions. Due to its easily biodegradable nature, rich nutrient availability and high moisture content, FW is regarded as favorable substrate for anaerobic digestion (AD). Both waste disposal and energy recovery can be fulfilled during AD of FW. Volatile fatty acids (VFAs) which are the products of the first-two stages of AD, are widely applied in chemical industry as platform chemicals recently. Concentration and distribution of VFAs is the result of acidogenic metabolic pathways, which can be affected by the micro-environment (e.g. pH) in the digester. Hence, the clear elucidation of the acidogenic metabolic pathways is essential for optimization of acidogenic process for efficient product recovery. This review summarizes major acidogenic metabolic pathways and regulating strategies for enhancing VFAs recovery during acidogenic fermentation of FW.
Process Biochemistry, 2018
The use of microbial consortia and industrial effluents for the production of biohydrogen by dark fermentation is seen as a key strategy in an attempt to overcome the economic and technical drawbacks of this potential technology. Three mesophilic microbial consortia were sampled and identified. Fermentation was carried out in a vinasse-based medium supplemented with pure or complex carbon sources under different conditions of H 2 partial pressure. Consortia LPBAH1 and LPBAH2 were predominantly composed of Oxalobacteraceae and Lactobacillaceae, while LPBAH3 was rich in sporulating Lactobacillaceae (> 96%). Each consortium presented specificities related to biohydrogen and VFAs production: (i) the highest biohydrogen yield was achieved with LPBAH1 (> 50% Oxalobacteraceae) in a vinasse medium supplemented with sugarcane juice (1.59 ± 0.21 mol H2 /mol glucose); (ii) The lower H 2 yields were achieved with LPBAH3, which otherwise produced the highest amount of butyric acid (up to 10 g L −1); (iii) LPBAH2 presented great stability in H 2 production in different conditions of H 2 partial pressure.
Environmental Earth Sciences, 2015
Anaerobic microorganisms involved in butyric acid production have inherent requirements for trace metals. The inefficiency of trace metals in an acidogenic reactor can result in the poor yield of butyric acid. However, trace metal requirements for butyric acid production are not often reported in literature. Therefore, in order to enhance butyric acid production, a novel technique was adopted in this paper, i.e., trace metals including zinc (Zn), cuprum (Cu), cobalt (Co), manganese (Mn) and ferrum (Fe) were added into the fermentation substrate to favor the butyric acid-producing bacteria. Firstly, the effect of each trace metal on butyric acid production was investigated, respectively. And then, response surface methodology combined with Box-Behnken design was used to optimize the mixing conditions of the five trace metals. The results showed that each trace metal had the potential to enhance butyric acid production, and the influence was as follows: Fe [ Mn [ Co & Zn [ Cu. The optimal mixing conditions of these five trace metals were found to be 0.112 % Fe, 0.005 % Co, 0.0055 % Zn, 0.0042 % Cu and 0.112 % Mn, under which, the concentration of butyric acid reached 5102 mg L-1. The maximum yield of butyric acid arrived at 310 mg g-1 VS added, and its percentage in the total volatile fatty acids was 72.1 %. The fitting result came up to 99.6 % between the model prediction and the experiment value, which indicated that the established polynomial regression model was feasible. Protein was the main contributor for the butyric acid production. The terminal restriction fragment length polymorphism analysis combining with sequencing showed that the addition of Fe, Co, Cu, Zn and Mn with the optimal contents could induce the growth of Clostridium as the dominant bacterial genus in the process of butyric acid production.
2021
Acidogenic fermentation of wastes produces volatile fatty acid (VFA)-rich streams that can be used as low-cost carbon sources for polyhydroxyalkanoate (PHA) production. In this study, an inoculum collected from an anaerobic reactor of a municipal WWTP was conditioned to suppress methanogenic activity. The heat-shock conditioning method of the inoculum proved to be more efficient than acid and alkaline conditioning methods for methanogen inhibition. Then, the pre-conditioned inoculum was used to determine the acidogenic potential of different wastes: three waste activated sludge (WAS) samples generated at different sludge retention times (SRTs, 2, 7 and 14 days), olive mill wastewater (OMW), glycerol, apple pomace (AP) and winterization oil cake (WOC). Batch tests were performed in quintuplicate at 37°C and pH 7. A higher degree of acidification was observed for high-rate activated sludge (2 days of SRT) (69%), followed by olive mill wastewater (OMW) (43%), while the lowest was for g...
Analysis of the key enzymes of butyric and acetic acid fermentation in biogas reactors
This study aimed at the investigation of the mechanisms of acidogenesis, which is a key process during anaerobic digestion. To expose possible bottlenecks, specific activities of the key enzymes of acidification, such as acetate kinase (Ack, 0.23–0.99 U mg−1 protein), butyrate kinase (Buk, < 0.03 U mg−1 protein) and butyryl-CoA:acetate-CoA transferase (But, 3.247.64 U mg−1 protein), were determined in cell free extracts of biogas reactor content from three different biogas reactors. Furthermore, the detection of Ack was successful via Western blot analysis. Quantification of corresponding functional genes encoding Buk (buk) and But (but) was not feasible, although an amplification was possible. Thus, phylogenetic trees were constructed based on respective gene fragments. Four new clades of possible butyrateproducing bacteria were postulated, as well as bacteria of the genera Roseburia or Clostridium identified. The low Buk activity was in contrast to the high specific But activity in the analysed samples. Butyrate formation via Buk activity does barely occur in the investigated biogas reactor. Specific enzyme activities (Ack, Buk and But) in samples drawn from three different biogas reactors correlated with ammonia and ammoniumconcentrations (NH3 and NH4+-N), and a negative dependency can be postulated. Thus, high concentrations of NH3 and NH4+-N may lead to a bottleneck in acidogenesis due to decreased specific acidogenic enzyme activities.
Acidogenic fermentation towards valorisation of organic waste streams into volatile fatty acids
Anaerobic acidification of eight organic streams (cheese whey, sugarcane molasses, organic fraction of municipal solid wastes (OFMSW), glycerol, soapy slurry, winery wastewater, olive mill effluent, and landfill leachate) was evaluated in batch experiments to determine their acidogenic potential and examine the composition of the produced volatile fatty acids (VFA). Cheese whey, molasses and OFMSW presented the highest acidogenic potentials (0.3 to 0.4 gVFA per g of chemical oxygen demand fed, COD fed) with the predominance of acetic, n-butyric and propionic acids. A further experimental set was applied to cheese whey, by varying food-to-microorganism ratio (F/M) and initial alkalinity. Maximisation of VFA production (up to 0.63 gVFA g-1 COD fed) was obtained for an initial alkalinity of 5-7 g L-1 as CaCO 3 and F/M ratios of 2-4 gCOD g-1 VSS. Moreover, it was demonstrated that low F/M ratios combined with high alkalinity supply can shift the VFA profile by increasing the production of pro pionic and n-valeric acids. The results are useful towards optimal designs for acido genic processes based on the composition of the VFA produced, since the control of the acidification products is crucial for valorisation in some applications.