Accumulation Of Propionic Acid Research Articles

Study on the treatment of corn alcohol wastewater by the internal circulation anaerobic reactor.

To comprehensively assess the efficacy of employing the internal circulation (IC) anaerobic reactor for corn alcohol wastewater treatment and investigate its feasibility, this study focused on anaerobic digestion parameters, energy balance, and the composition of the prokaryotic microbial community. During the operation of the reactor, the hydraulic retention time was progressively reduced from 4.8 to 1.6 days while achieving an average organic loading rate of 12.46 kg chemical oxygen demand (COD)/(m3·d). Moreover, the removal rate of COD exceeded 98%, and the energy balance (ΔE) reached 10.29 kJ/g fed COD. The initial manifestation of organic acidosis in the reactor was a decline in gas production, which is primarily caused by propionic acid accumulation. The subsequent analysis revealed a high diversity of prokaryotes in granular sludge, with the predominant archaea primarily involved in methane production through the acetic acid pathway. The IC anaerobic reactor shows exceptional performance in treating corn alcohol wastewater by optimizing its operating conditions. Energy balance analysis confirmed the feasibility of the process. The findings of this study may offer valuable insights for optimizing control strategies and engineering applications.

Metatranscriptome revealed how carbon brush addition affected the fermentation of food wastewater in the low-temperature environment

Improving the anaerobic digestion (AD) performance in low-temperature environments has become a key factor in the development of waste treatment and resource recovery in cold regions. The utilization of external carriers to form a biofilm is the simplest and most practical way to enhance the psychrophilic AD performance in cold regions. In this study, the effect of carrier addition on the fermentation performance of low-temperature (15 ± 2 °C) food wastewater was investigated by forming biofilms with carbon brushes. The results showed that although the biofilm formation enhanced methane yields (15.24%), it also caused more accumulation of propionic acid (306.99–626.89 mg/L), and the concentration of acetic acid (86.78–254.71 mg/L) was relatively low. The microbial community revealed the highest abundance of the fermentative bacterium Firmicutes and the carbon brush carrier significantly increased its relative abundance (23.74%). Metatranscriptomic sequencing revealed that the abundance level of Clostridium, Bacteroides, Sedimentibacter and Pelotomaculum was the highest, reaching 80% in all groups. In addition, the abundance level of electroactive microorganisms in biofilms was higher, while the fermentation bacteria and methanogens were lower. This showed that biofilm can enrich more electroactive microorganisms, and granular sludge needs to enrich more fermentation bacteria and methanogens to ensure metabolic activity. Further studies have found that carbon metabolism had the highest activity (27.86%–30.39%) and H+-transporting ATPase (atp) was the most dominant functional enzyme (85.50%–86.65%) involved in electron transport in low-temperature fermentation of food wastewater. Interestingly, these expression levels of active granular sludge were higher than the biofilm formed by carbon brushes. Meanwhile, analysis of the methanogenic pathway found that active granular sludge tends to be directly metabolized to realize acetate to acetyl-CoA by acetyl-CoA synthetase (ACSS), while biofilms were not significantly different in the two metabolic pathways of acetate. These results deepen the understanding of treating low-temperature food wastewater.

Neonatal Propionic Acidemia: A Case Report in the Sri Lanka

Propionic acidemia (aciduria) is a rare autosomal recessive inherited metabolic disorder that is caused by a defective form of the propionyl-coenzyme A (COA) carboxylase enzyme, which results in the accumulation of propionic acid. If the patient is having conditions with increased metabolic demand followed by catabolism, they can present as acute deterioration. Clinical features usually start shortly after birth, and rare cases are present in young adulthood. This disorder most commonly is characterized by episodic decompensation with dehydration, lethargy, nausea, and vomiting. Early identification and initial management are crucial to prevent the mortality and morbidity of patients. Our case is the first baby of consanguineous parents, presented with vomiting, Poor feeding, and severe dehydration on day four of life. In developed countries, early detection is done with newborn screening, but in Sri Lanka like third world countries it is not possible due to poor resources. The take-home message is if a newborn who is a product of consanguineous parents presented with non-specific symptoms, always think about the metabolic disorders which need urgent intervention to save the child from acute and long-term complications.

Mediated anaerobic system performance, co-metabolizing flora and electron transfer by graphene oxide supported zero-valent iron composite

To enhance the traditional anaerobic treatment process, zero-valent iron (Fe0) and graphene oxide (GO) have recently been used and studied. However, there are drawbacks in using GO and Fe0 alone. In this study, Fe0/GO composite was utilized in anaerobic treatment of high strength wastewater to compensate for the drawbacks, and the promoting effects and the mechanism were investigated. The results verified that Fe0/GO improved COD removal rate and gas production which reached 91.8 % and 511 mL/12 h, respectively, and a better sludge flocculation performance was obtained. Furthermore, the fermentation type was optimized due to alteration of pH and oxidation-reduction potential by Fe0/GO, resulting in increment of acetic acid production and reduction of propionic acid accumulation. A detailed microbial characterization indicated that Fe0/GO had a significant effect on hydrotrophic methanogens (Methanofastidiosum and Methanofastidiosales), increasing from 1.79 % to 24.11 %. The distribution of hydrolytic fermentation bacteria, acetogenic bacteria and methanogens was more balanced and more diverse in the Fe0/GO system, indicating that a stable co-metabolizing microbial community was maintained. Moreover, the highest electron transport system activity and Fe2+ and Fe3+ concentration demonstrated that Fe0/GO could improve the intracellular and interspecific electron transfer. The conductivity, current response, cyclic voltammetry area were the highest and the internal resistance was the lowest, indicating that Fe0/GO could improve the extracellular electron transfer. The stable co-metabolizing microbial community and efficiency intra/extracellular electron transfer promoted the anaerobic wastewater treatment. This study could provide theoretical support for the practical application of developing technologies for anaerobic wastewater treatment.

Potential of hydrochar/pyrochar derived from sawdust of oriental plane tree for stimulating methanization by mitigating propionic acid inhibition in mesophilic anaerobic digestion of swine manure

VFAs accumulation in anaerobic digestion systems can lead to disturbance of the acid base balance, which has brought major challenges for methane production. Meanwhile, less research explored the potential of biochar derived from wood wastes of oriental plane tree (Platanus orientalis L.) for stimulating methanization in mesophilic anaerobic digestion. In this study, the effects of pyrochar and hydrochar derived from sawdust of oriental plane tree on mesophilic anaerobic digestion of swine manure were compared for the first time. Fourier infrared transform analysis indicated that more functional groups existed on the surface of hydrochar, whereas higher ash content and BET specific surface area were found in pyrochar. The maximum methane production rate during anaerobic digestion was observed in the pyrochar treatment, which increased by 59.5% compared with the control without biochar. Although stimulative effects on dissolved organic carbon and volatile fatty acids production were both observed in the pyrochar and hydrochar treatments, the pyrochar treatment was much easier to trigger multipath methanogenesis and direct interspecific electron transport and subdue propionic acid accumulation compared to the hydrochar treatment. Moreover, redundancy analysis indicated that the variations in acetic acid and dissolved organic carbon were mostly associated with microbial succession. These results suggest that pyrochar has better promoting effects than HC in terms of methane generation and propionic acid inhibition alleviation owing to its special porous structures, functional groups (e.g., C=O, C–O and O–H), and physicochemical properties. These excellent properties play a greater role in recruiting functional archaea and bacteria to regulate the levels of volatile fatty acids and dissolved organic carbon to enhance the methane yield of anaerobic digestion. This study provides novel and valuable information for further engineering applications of pyrochar and hydrochar derived from sawdust of oriental plane tree in energy production and environmental waste treatment.

Impact of Bifidobacterium longum NSP001 on DSS-induced colitis in conventional and humanised mice

Most scientific investigations regarding inflammatory bowel disease (IBD) pathogenesis or therapeutic strategies use dextran sulfate sodium (DSS)-induced models performed on mice. However, differences between human and animal microbiota may confound the data reproducibility from rodent experiments to clinical trials. In this study, the intervention effects of Bifidobacterium longum NSP001 on DSS-induced colitis were investigated using mice colonized with either native or humanised microbiota. Disorders in disease activity index (DAI), morphology and histology of colon tissue, intestinal permeability, and secretion of MPO, TNF-α and IL-6 were ameliorated by daily intake of live B. longum NSP001 cells in both conventional and humanised colitis mice. But the abnormal thymus index, and colonic production of ZO-1 and iNOS were improved only in colitis mice treated with B. longum NSP001 and humanised microbiome. The accumulation of acetic acid and propionic acid in colon microbiome, and the optimization of primary bile acid biosynthesis and glycerophospholipid metabolism pathways in cecum commensals were likely to explain the beneficial effects of B. longum NSP001. These data revealed that intestinal microbiome baseline would possibly affect the manifestation features of interventions by probiotics or dietary components and highlighted the necessity to include humanised microbiome while investigating potential therapeutic strategies based on rodent models.

Start-up of the mesophilic anaerobic co-digestion of two-phase olive-mill waste and cattle manure using volatile fatty acids as process control parameter

In this work, the start-up and stabilization stages of mesophilic anaerobic co-digestion of 2POMW and CM in a semi-continuously fed stirred tank reactor (SSTR) were analyzed. Volatile fatty acids (VFAs) were monitored and used as the main control parameter for the start-up and stabilization stages, as well as to evaluate the potential inhibition episodes. The results showed that accumulation of propionic acid was the key factor in the inhibition of the methanogenic phase, leading to process imbalance. To avoid the problems associated with inhibition by high VFA concentrations, several reinoculations were performed using a suitable inoculum adapted to VFA degradation. The start-up phase was carried out in batch conditions for 97 days, reaching a final concentration of propionic acid of 12.77 mg/L. From that moment, the reactor was fed in a semi-continuous mode with a hydraulic retention time (HRT) of 40 days. A total period of 140 days was required to achieve a stable performance of the reactor with a methane productivity of 0.34 LCH4/LRd.

Influence of the initial proportion of carbohydrates, proteins, and lipids on biohydrogen production by dark fermentation: A multi-response optimization approach

The present study investigated the effect of the initial proportions of carbohydrates, proteins and lipids within the substrate on the resulting biohydrogen productivity by dark fermentation. Organic matter removal and the related metabolic by-products generated during the process were also assessed. The results obtained showed that initial substrate composition in terms of carbohydrates, proteins and lipids has a significant effect on maximal potential hydrogen production (Hmax), hydrogen production rate (Rmax), hydrogen yield (YH2) and metabolites distribution. Tests with proteins and lipids as unique substrate did not produce H2. A simplex-centroid design (SCD) and compositional data analysis of the substrate was used to determine the best condition to convert the substrate into H2. Hmax, Rmax and YH2 were significantly increased using an initial proportion of 56% carbohydrates (15 g/L), 22% proteins (6 g/L), and 22% lipids (6 g/L), which was concomitant with the generation of acetic and butyric acids. Protein and lipid proportions higher than 29% and lower than 12% led to decreased Hmax, Rmax and YH2 values with a consequent accumulation of propionic acid.

Can Salt-Tolerant Sludge Mitigate the Salt Inhibition to Acidogenic Fermentation of Food Waste? Insight Into Volatile Fatty Acid Production and Microbial Community

For treatment of saline wastewater, the feasible approach to mitigate the salt inhibition is using the acclimated salt-tolerant sludge. The aim of this work was to verify if the use of the acclimated sludge (AS) also could alleviate salinity stress on acidogenic fermentation of food waste (FW) under saline environment. The responses of volatile fatty acid (VFA) production and the microbial community to salt stress were investigated. Results showed that VFA production was reduced by high salinity (30 g/L and 70 g/L NaCl) compared with the control (0 g/L NaCl), especially for groups inoculated with the AS, whereas inoculating with the non-acclimated sludge (non-AS) caused less reduction. The impact of salinity was seen on VFA production with accumulation of more propionic acid and acetic acid along with traces of butyric acid. Significant shift on microbial community composition occurred upon biomass exposure to salt. The microbial communities of the non-AS and AS groups at the same NaCl concentrations converged over time. The non-AS groups contained a more proportion of the phyla Bacteroidetes, Atribacteria and Chloroflexi at high salt levels. These findings demonstrate that the non-AS was more conducive to VFA production due to the presence of higher proportions of hydrolytic and fermenting bacteria.

GO/iron series systems enhancing the pH shock resistance of anaerobic systems for sulfate-containing organic wastewater treatment.

In this study, the effect of pH shock during the treatment of sulfate-containing organic wastewater was investigated using an anaerobic fermentation system reinforced with graphene oxide (GO)/iron series systems. The results show that the anaerobic system with the GO/iron series systems exhibited enhanced resistance to pH shock. Among them, the GO/Fe0 system had the strongest resistance to pH shock, the systems of GO/Fe3O4 and GO/Fe2O3 followed close behind, while the blank system performed the worst. After pH shock, the CODCr removal rate, SO42− removal rate, and gas production of the GO/Fe0 group were significantly improved compared with those of the control group by 51.0%, 65.3%, and 34.6%, respectively, while the accumulation of propionic acid was the lowest. Further, detailed microbial characterization revealed that the introduction of the GO/iron series systems was beneficial to the formation of more stable anaerobic co-metabolic flora in the system, and the relative abundance of Geobacter, Clostridium, Desulfobulbus and Desulfovibrio increased after acidic and alkaline shock.

Effects of Lipase Addition, Hydrothermal Processing, Their Combination, and Co-Digestion with Crude Glycerol on Food Waste Anaerobic Digestion

To enhance anaerobic fermentation during food waste (FW) digestion, pretreatments can be applied or the FW can be co-digested with other waste. In this study, lipase addition (LA), hydrothermal pretreatment (HTP), and a combination of both methods (HL) were applied to hydrolyze organic matter in FW. Furthermore, the effects of crude glycerol (CG), which provided 5%, 10%, and 15% of the volatile solids (VS) as co-substrate (denoted as CG5, CG10, and CG15, respectively), on the anaerobic digestion of FW were assessed. With an increasing proportion of CG in the co-digestion experiment, CG10 showed higher methane production, while CG15 negatively affected the anaerobic digestion (AD) performance owing to propionic acid accumulation acidifying the reactors and inhibiting methanogen growth. As the pretreatments partially decomposed hard-to-degrade substances in advance, pretreated FW showed a stronger methane production ability compared with raw FW, especially using the HL method, which was significantly better than co-digestion. HL pretreatment was shown to be a promising option for enhancing the methane potential value (1.773 NL CH4/g VS) according to the modified Gompertz model.

Carboxylic acids production via anaerobic fermentation: Microbial communities’ responses to stepwise and direct hydraulic retention time decrease

Carboxylic acids, traditionally produced from fossil fuels, might be generated from renewable biomass resources via anaerobic fermentation. Considering that the microbial activity of this bioprocess is ruled by the imposed hydraulic retention time (HRT), this investigation explored the relationship between process stability and microbial community. Stepwise and direct HRT reduction strategies were assessed in terms of waste bioconversion into volatile fatty acids (VFAs). Microbial community dynamics revealed a microbial specialization along the HRT decrease. The direct implementation of low HRT resulted in drastic microbial fluctuations, leading to process failure at HRT below 6 days. Stepwise strategy for HRT reduction favored microbial adaptation, supporting maximum bioconversions efficiencies (32 % VFACOD/tCODin) at low HRT values (HRT 4 days). Microbial similarity analysis revealed Clostridiales, Lactobacillales and Bacteroidales orders as keystone microorganisms involved in VFAs production, being responsible for protein degradation and propionic acid accumulation.

Operational load enhancement for an anaerobic membrane bioreactor through ethanol fermentation pretreatment of food waste

Anaerobic digestion (AD) of food waste (FW) tends to result in the accumulation of volatile fatty acids (VFA), especially a large quantity of propionic acid that is inevitably produced. Propionic acid has a significant inhibitory effect on AD at a concentration far lower than acetic acid. Therefore, anaerobic digestion cannot be operated at an excessively high load. We proposed an AD system that used a considerable amount of starch-rich food waste for ethanol fermentation as a pretreatment and reported that it improved methane concentration in biogas with a low propionic acid accumulation even under high-load operation. This study examined whether ethanol fermentation pretreatment (EP) of food waste can contribute to high-load operation on AD using an anaerobic membrane bioreactor (AnMBR). This involved a sequential bath experiment using FW that was saccharized before fermentation to ethanol. The results are compared with those for FW without pretreatment. The organic loading rate (OLR) was stepwise increased to 43.5 g COD/L/d by increasing the feed OLR, the hydraulic retention time (HRT) was six days and methane content was 71%–74%, which is thrice the capability of the control series and the highest load in the reports of medium temperature AD of FW. Furthermore, the primary methanogens were tolerant to ammonia inhibition. Correspondingly, the ammonium produced improved the buffering capacity of AD at high load. Functional archaeal and bacterial communities in the two reactors were examined. The abundance of hydrogenotrophic methanogens in AnMBR are determined to highlight the impact of the EP for FW disposal through 16S rRNA sequence analysis. Because there were multiple methanogens that use hydrogen, the higher decomposition of the substrate was attributable to the maintenance of a lower hydrogen partial pressure. It contributed to create a virtuous cycle with the EP. This study demonstrates the performance of the EP during high loading and long-term AD operation using an AnMBR; moreover, ultra-high load is achieved by changing the metabolic pathway.

Effect of nano-magnetite on the propionic acid degradation in anaerobic digestion system with acclimated sludge

In this study, a batch of acid-tolerant inoculation sludge was domesticated as inoculum, and different concentrations of nano-magnetite were added to the propionic acid (PA) anaerobic digestion system to explore its effect on the PA degradation. It was found the PA degradation rates of nano-magnetite groups were 10.96–74.62% higher than the control group without magnetite in the 6th day, especially with the dosage of 100 mg/L. Microbial community analysis showed some potential DIET participants of Chloroflexi, Proteobacteria and Bacteroidetes had the highest abundance, while metabolite analysis showed that nano-magnetite promoted the transformation of malic acid to oxaloacetic acid and the PA disproportionation to butyric acid. It indicated that nano-magnetite could effectively promote the early degradation of PA in the sludge acclimation system by accelerating DIET or PA disproportionation, so as to prevent the PA accumulation, which could provide reference for the acid accumulation regulation of anaerobic digestion system.

Biodeterioration kinetics and microbial community organization on surface of cementitious materials exposed to anaerobic digestion conditions

Anaerobic digestion is a process that can produce renewable energy through the fermentation of biodegradable biomass. Industrial anaerobic digestion tanks are usually made of concrete but the production of various aggressive compounds (CO2, NH4+ and volatile fatty acids) during the microbial fermentation leads to deterioration of the concrete structure. In addition, the formation of a microbial biofilm on the cementitious material surface could generate even more intense biodeterioration. The objective of this study is to gain a better understanding of the involvement of biofilm in the biodeterioration of cementitious materials during an anaerobic digestion process. More specifically, the study focuses on the heterogeneity of microbial populations within the biofilm and the reactive medium in anaerobic digestion. Laboratory scale anaerobic bioreactors mimicking the industrial anaerobic digestion medium were constructed and CEM I cement pastes were immersed in this medium for 2, 3, 4, 5, 10 and 15 weeks. The biodeterioration of the cement pastes was evaluated by determining the deteriorated thickness. The aggressive compounds in the medium were quantified. The biofilm attached to the surface of the cement pastes was analyzed using 16 s rRNA gene sequencing. To evaluate the heterogeneity of the biofilm, the growth of biofilm layers was successively caused to stall by using two distinct biofilm removal techniques. Three microbial fractions were defined: planktonic microorganisms, and the microorganisms within the biofilm that were loosely and strongly attached. The results showed that the planktonic lifestyle was more associated with microorganisms producing methane and consuming volatile fatty acids, while the biofilm was more associated with bacteria producing acids, mainly members of the Clostridium genus. A microbial community shift due to a reversible propionic acid accumulation during the first 5 weeks was also observed. In addition, no major differences were spotted between the loosely and strongly attached biomass, indicating homogeneity in the two layers of the biofilm. These results suggest that the biofilm could increase the biodeterioration of concrete since volatile fatty acids could be produced in massive quantities near the surface of the cement samples by the acidogenic microbial population more present within the biofilm.

The effect of propionic acid accumulation on methane production in dry mesophilic anaerobic fermentation

The dry anaerobic digestion performances were investigated at the temperature of 35±1°Cwith addition of propionic acid at different concentrations in five lab-scale reactors (R1-R5) to investigate the effect of propionic acid accumulation on methane production in dry mesophilic anaerobic digestion. And the volatile fatty acids, biogas and microbial community were detected. The active of microbial community and the methane generation would be inhibited when the propionic acid exceeded 30 gL1, which affected not only syntrophic propionate-oxidizing bacteria but also acetate-utilizing methanogens. Eubacteria decreased sharply accompany with the higher concentration of propionic in R4 and R5. The relative abundance of acetoclastic methanogens was directly correlated with volatile solids removals and methane generation in dry anaerobic reactors. Otherwise, the quantity of syntrophic propionate-oxidizing bacteria was positively linear correlated with propionic acid when the concentration was below 30 gL1. The methanogenic bacteria activity in R3 was the best with the methane yield of 27.01 mLCH4 g-1 VS d-1. The results suggested that appropriate propionate could enhance methane production in the dry anaerobic fermentation.

Microbial electrolysis enhanced bioconversion of waste sludge lysate for hydrogen production compared with anaerobic digestion

Waste sludge lysate was produced by dehydration after pyrolysis of waste activated sludge. In addition to dominant components such as protein, polysaccharide, and volatile fatty acids (VFAs), it also contained melanoidins, which produced from Maillard reaction. The inclusion of melanoidins will lead to poor biological degradation in conventional anaerobic digestion (AD). While microbial electrolysis cell (MEC) was proved an enhanced degradation of complex organic matter for hydrogen production. The results showed that under high concentration conditions, conventional AD caused the accumulation of propionic acid and slowed down the use of acetic acid, but MEC overcame the defects and increased the chemical oxygen demand (COD) removal efficiency by 40.33%, and achieved average hydrogen production rate (0.15 ± 0.05 L L−1 day−1), which was 79 times that of AD system (0.0019 ± 0.0009 L L−1 day−1). Therefore, MEC can enhanced biodegradation of the waste sludge lysate for high hydrogen production.

Effect of liquid digestate recirculation on biogas production and enzyme activities for anaerobic digestion of corn straw

To accelerate the degradation of substrate, 50% liquid digestate recirculation (LDR) was used in the anaerobic digestion (AD) of corn straw. The effects of recirculation on the enzyme activities and biogas production were investigated by comparing with control reactor (ReactorCK). During the AD process, the fermentation system with 50% LDR was more stable. The average biogas and methane production in ReactorLDR were 7,891 mL·d-1 and 347 mL CH4·g-1 VSadded·d-1 respectively. The total volatile fatty acids (TVFAs) concentration in the two reactors both increased at first and then decreased with time. The LDR made the VFAs accumulation significant, especially propionic acid accumulation in 4 ∼ 16 days. The maximum peak value of cellulase, xylanase, dehydrogenase and coenzyme F420 activities in ReactorLDR were 0.51 mg·g-1·h-1, 0.29 mg·g-1·h-1, 4.88 mL·g-1·h-1 and 6.69 μmol·L-1, respectively, which were higher than that in ReactorCK. With or without recirculation, the concentration of TVFAs was positively correlated with cellulase, xylanase and dehydrogenase activities, while was negatively correlated with coenzyme F420 activity. Besides, a very significant correlation existed between hydrolase and dehydrogenase activities and daily biogas production in ReactorCK. And the peaks of cellulase, xylanase and dehydrogenase activities appeared ahead of the peak of daily biogas production with the LDR.

Direct Fermentative Hydrogen Production from Cellulose and Starch with Mesophilic Bacterial Consortia.

Hydrogen produced from lignocellulose biomass is deemed as a promising fuel of the future. However, direct cellulose utilization remains an issue due to the low hydrogen yields. In this study, the long-term effect of inoculum (anaerobic sludge) heat pretreatment on hydrogen production from untreated cellulose and starch was evaluated during repeated batch processes. The inoculum pretreatment at 90°C was not sufficient to suppress H2 consuming bacteria, both for starch and cellulose. Although hydrogen was produced, it was rapidly utilized with simultaneous accumulation of acetic and propionic acid. The pretreatment at 100°C (20 min) resulted in the successful enrichment of hydrogen producers on starch. High production of hydrogen (1.2 l H2/lmedium) and H2 yield (1.7 mol H2/molhexose) were maintained for 130 days, with butyric (1.5 g/l) and acetic acid (0.65 g/l) as main byproducts. On the other hand, the process with cellulose showed lower hydrogen production (0.3 l H2/lmedium) with simultaneous high acetic acid (1.4 g/l) and ethanol (1.2 g/l) concentration. Elimination of sulfates from the medium led to the efficient production of hydrogen in the initial cycles – 0.97 mol H2/molhexose (5.93 mmol H2/gcellulose). However, the effectiveness of pretreatment was only temporary for cellulose, because propionic acid accumulation (1.5 g/l) was observed after 25 days, which resulted in lower H2 production. The effective production of hydrogen from cellulose was also maintained for 40 days in a repeated fed-batch process (0.63 mol H2/molhexose).

Carglumic Acid Contributes to a Favorable Clinical Course in a Case of Severe Propionic Acidemia

Propionic acidemia (PA) is manifested as an abnormal accumulation of propionic acid and its metabolites, including methylcitrate, 3-hydroxypropionic acid, and propionylglycine, and is caused by a defect of propionyl-CoA carboxylase. PA is complicated by acute life-threatening metabolic crises, which are precipitated by a catabolic state and result in multiple organ failure or even death, if untreated. A neonate with PA recovered from the first metabolic crisis 3 days after birth but developed a second metabolic crisis during the recovery phase. This patient was considered to have severe PA and was accordingly given carglumic acid treatment in combination with carnitine supplementation and protein restriction, which was expected to prevent a recurrent metabolic attack. The patient did not develop hyperammonemia after receiving carglumic acid and was never hospitalized. Moreover, she did not present with acidosis even during viral infection. At 26 months of age, she led a stable life while receiving carglumic acid and regular rehabilitation. Carglumic acid treatment in combination with carnitine supplementation and protein restriction prevented metabolic decompensation, which would have otherwise required hospitalization, and resulted in improved quality of life and developmental outcomes.