ABSTRACT
This work aimed to evaluate the lovastatin (Lv) production by solid-state fermentation (SSF) from selected crop residues, considering the post-fermented residues as feed supplements for ruminants. The SSF was performed with two substrates (wheat bran and oat straw) and two A. terreus strains (CDBB H-194 and CDBB H-1976). The Lv yield, proximate analysis, and organic compounds by GC-MS in the post-fermented residues were assessed. The combination of the CDBB H-194 strain with oat straw at 16 d of incubation time showed the highest Lv yield (23.8 mg/g DM fed) and the corresponding degradation efficiency of hemicellulose + cellulose was low to moderate (24.1%). The other three treatments showed final Lv concentrations in decreasing order of 9.1, 6.8, and 5.67 mg/g DM fed for the oat straw + CDBB H-1976, wheat bran + CDBB H-194, and wheat bran + CDBB H-1976, respectively. An analysis of variance of the 22 factorial experiment of Lv showed a strong significant interaction between the strain and substrate factors. The kinetic of Lv production adequately fitted a zero-order model in the four treatments. GC-MS analysis identified only a couple of compounds from the residues fermented by A. terreus CDBB H-194 (1,3-dipalmitin trimethylsilyl ether in the fermented oat straw and stearic acid hydrazide in the fermented wheat bran) that could negatively affect ruminal bacteria and fungi. Solid-state fermentation of oat straw with CDBB H-194 deserves further investigation due to its high yield of Lv; low dietary proportions of this post-fermented oat straw could be used as an Lv-carrier supplement for rumen methane mitigation.
ABSTRACT
Methane from enteric fermentation is the gas with the greatest environmental impact emitted by ruminants. Lovastatin (Lv) addition to feedstocks could be a strategy to mitigate rumen methane emissions via decreasing the population of methanogenic archaea (MA). Thus, this paper provides the first overview of the effects of Lv supplementation, focusing on the inhibition of methane production, rumen microbiota, and ruminal fermentation. Results indicated that Lv treatment had a strong anti-methanogenic effect on pure strains of MA. However, there are uncertainties from in vitro rumen fermentation trials with complex substrates and rumen inoculum.Solid-state fermentation (SSF) has emerged as a cost-effective option to produce Lv. In this way, SSF of agricultural residues as an Lv-carrier supplement in sheep and goats demonstrated a consistent decrease in ruminal methane emissions. The experimental evidence for in vitro conditions showed that Lv did not affect the volatile fatty acids (VFA). However, in vivo experiments demonstrated that the production of VFA was decreased. Lv did not negatively affect the digestibility of dry matter during in vitro and in vivo methods, and there is even evidence that it can induce an increase in digestibility. Regarding the rumen microbiota, populations of MA were reduced, and no differences were detected in alpha and beta diversity associated with Lv treatment. However, some changes in the relative abundance of the microbiota were induced. Further studies are recommended on: (i) Lv biodegradation products and stability, as well as its adsorption onto the solid matter in the rumen, to gain more insight on the "available" or effective Lv concentration; and (ii) to determine whether the effect of Lv on ruminal fermentation also depends on the feed composition and different ruminants.
ABSTRACT
The purpose of this work was to produce iron nanoparticles (Fe-NP) by microbial pathway from anaerobic bacteria grown in anaerobic fluidized bed reactors (AnFBRs) that constitute a new stage of a waste-based biorefinery. Bioparticles from biological fluidized bed reactors from a biorefinery of organic fraction of municipal solid wastes (that produces hydrolysates rich in reducing sugars) were nanodecorated (embedded nanobioparticle or nanodecorated bioparticle, ENBP) by biological reduction of iron salts. Factors "origin of bioparticles" (either from hydrogenogenic or methanogenic fluidized bed reactor) and "type of iron precursor salt" (iron chloride or iron citrate) were explored. SEM and high-resolution transmission electron microscopy (HRTEM) showed amorphous distribution of nanoparticles (NP) on the bioparticles surface, although small structures that are nanoparticle-like could be seen in the SEM micrographs. Some agglomeration of NPs was confirmed by DLS. Average NP size was lower in general for NP in ENBP-M than ENBP-H according to HRTEM. The factors did not have a significant influence on the specific surface area of NPs, which was high and in the range 490 to 650 m2 g-1. Analysis by EDS displayed consistent iron concentration 60-65% iron in nanoparticles present in ENBP-M (bioparticles previously grown in methanogenic bioreactor), whereas the iron concentration in NPs present in ENBP-H (bioparticles previously grown in hydrogenogenic bioreactor) was more variable in a range from 8.5 to 62%, depending on the iron salt. X-ray diffraction patterns showed the typical peaks for magnetite at 35° (3 1 1), 43° (4 0 0), and 62° (4 0 0); moreover, siderite diffraction pattern was found at 26° (0 1 2), 38° (1 1 0), and 42° (1 1 3). Results of infrared analysis of ENBP in our work were congruent with presence of magnetite and occasionally siderite determined by XRD analysis as well as presence of both Fe+2 and F+3 (and selected satellite signal peaks) observed by XPS. Our results on the ENBPs hold promise for water treatment, since iron NPs are commonly used in wastewater technologies that treat a wide variety of pollutants. Finally, the biological production of ENBP coupled to a biorefinery could become an environmentally friendly platform for nanomaterial biosynthesis as well as an additional source of revenues for a waste-based biorefinery.
Subject(s)
Iron , Nanoparticles , Bacteria, Anaerobic , Bioreactors , WastewaterABSTRACT
In this work, the parametric optimization of real domestic wastewater treated in an activated sludge sequencing batch reactor (SBR) was performed by means of the response surface methodology (RSM). The influences of influent organic matter concentration as chemical oxygen demand (CODinf), biomass concentration (Xs) and aeration time (t) on the COD, organic matter removal efficiency as COD (η) and sludge volume index (SVI) were determined to evaluate the performance of activated sludge SBR. The results showed that organic matter efficiency and maximum SVI were obtained at a t of 12 h, 300 mg L-1 of CODinf and 2000 mg L-1 of Xs. The SBR-activated sludge exhibited a η of 73% and an SVI of 119 mL g-1. Both values indicated a very good performance. Furthermore, the COD of the effluent under these conditions complied with Mexican regulations for wastewater discharged into water bodies.
Subject(s)
Bioreactors , Sewage/chemistry , Waste Disposal, Fluid/methods , Water Purification/methods , Biological Oxygen Demand Analysis , Biomass , Hydrocarbons/analysis , Hydrocarbons/isolation & purification , Models, Theoretical , Water Pollutants/analysis , Water Pollutants/isolation & purificationABSTRACT
A life cycle assessment (LCA) of a four-stage biorefinery concept, coined H-M-Z-S, that converts 1 t of organic fraction of municipal solid waste (OFMSW) into bioenergy and bioproducts was performed in order to determine whether it could be an alternative to common disposal of OFMSW in landfills in the Mexican reality. The OFMSW is first fermented for hydrogen production, then the fermentates are distributed 40 % to the methane production, 40 % to enzyme production, and 20 % to the saccharification stage. From hydrogen and methane, up to 267 MJ and 204 kWh of gross heat and electricity were produced. The biorefinery proved to be self-sustainable in terms of power (95 kWh net power), but it presented a deficit of energy for heating services (-155 MJ), which was partially alleviated by digesting the wastes from the bioproducts stages (-84 MJ). Compared to landfill, biorefinery showed lower environmental impacts in global warming (down to -128 kg CO2-eq), ozone layer depletion (2.96 × 10-6 kg CFC11-eq), and photochemical oxidation potentials (0.011 kg C2H4-eq). The landfarming of the digestates increased significantly the eutrophication impacts, up to 20 % below the eutrophication from landfilling (1.425 kg PO4-eq). These results suggest that H-M-Z-S biorefinery could be an attractive alternative compared to conventional landfilling for the management of municipal solid wastes, although new alternatives and uses of co-products and wastes should be explored and tested. Moreover, the biorefinery system would benefit from the integration into the market chain of the bioproducts, i.e., enzymes and hydrolysates among others.
Subject(s)
Biofuels/analysis , Bioreactors , Refuse Disposal/methods , Solid Waste/analysis , Waste Disposal Facilities , Fermentation , Hydrogen/analysis , Methane/analysis , MexicoABSTRACT
The present work evaluated the effects of (i) feeding a water contaminated with 80 mg/L PCE to bioreactors seeded with inoculum not acclimated to PCE, (ii) coupling ZVI side filters to bioreactors, and (iii) working in different biological regimes, i.e., simultaneous methanogenic aeration and simultaneous methanogenic-denitrifying regimes, on fluidized bed bioreactor performance. Simultaneous electron acceptors refer to the simultaneous presence of two compounds operating as final electron acceptors in the biological respiratory chain (e.g., use of either O2 or NO3- in combination with a methanogenic environment) in a bioreactor or environmental niche. Four lab-scale, mesophilic, fluidized bed bioreactors (bioreactors) were implemented. Two bioreactors were operated as simultaneous methanogenic-denitrifying (MD) units, whereas the other two were operated in partially aerated methanogenic (PAM) mode. In the first period, all bioreactors received a wastewater with 1 g chemical oxygen demand of methanol per liter (COD-methanol/L). In a second period, all the bioreactors received the wastewater plus 80 mg perchloroethylene (PCE)/L; at the start of period 2, one MD and one PAM were coupled to side sand-zero valent iron filters (ZVI). All bioreactors were inoculated with a microbial consortium not acclimated to PCE. In this work, the performance of the full period 1 and the first 60 days of period 2 is reported and discussed. The COD removal efficiency and the nitrate removal efficiency of the bioreactors essentially did not change between period 1 and period 2, i.e., upon PCE addition. On the contrary, specific methanogenic activity in PAM bioreactors (both with and without coupled ZVI filter) significantly decreased. This was consistent with a sharp fall of methane productivity in those bioreactors in period 2. During period 2, PCE removals in the range 86 to 97 % were generally observed; the highest removal corresponded to PAM bioreactors along with the highest dehalogenation efficiency (94 %). Principal component analysis as well as cluster analysis confirmed the trends mentioned above, i.e., the better performance of PAM over MD, and the unexpected no effect of the ZVI side filters on PCE removal and dehalogenation efficiencies. To the best of our knowledge, this is the first report on the combined treatment ZVI-biological of a water polluted with PCE, where the biological operation relied on simultaneous electron acceptors.
Subject(s)
Iron/chemistry , Tetrachloroethylene/metabolism , Waste Disposal, Fluid/methods , Aerobiosis , Bioreactors , Denitrification , Electrons , Filtration , Waste Disposal, Fluid/instrumentationABSTRACT
The objective of this work was to evaluate the degradation of the nonionic surfactant Tween 80 by a PCE-degrading consortium anchored in bioparticles of fluidized bed bioreactors used in onsite remediation. Batch lab-scale bioreactors were set with dominant denitrifying (DN), methanogenic (M), and aerobic (Ab) metabolisms. Tween 80 at 100 mg/L was the sole source of carbon and energy. Denitrifying bioreactors had the highest surfactant removal (70%). Tween removals in M and Ab bioreactors were 53 and 37%, respectively. Removals of organic matter (COD) closely followed the efficiencies reported for Tween. This strongly suggested that degradation of Tween 80 occurred. Positive consequences of Tween degradation in remediation are first, the surfactant will not become an environmental/health liability by remaining as a recalcitrant or toxic substance in aquifers or in treated effluents; and second, savings on aeration could be achieved by conducting Tween 80 degradation in anaerobic conditions, either DN or M.
Subject(s)
Biodegradation, Environmental , Groundwater/chemistry , Surface-Active Agents/chemistry , Tetrachloroethylene/chemistry , Water Pollutants, Chemical/chemistry , Polysorbates/chemistryABSTRACT
Cellulase (CMCase) and xylanase enzyme production and saccharification of sugar cane bagasse were coupled into two stages and named enzyme production and sugar cane bagasse saccharification. The performance of Cellulomonas flavigena (Cf) PR-22 cultured in a bubble column reactor (BCR) was compared to that in a stirred tank reactor (STR). Cells cultured in the BCR presented higher yields and productivity of both CMCase and xylanase activities than those grown in the STR configuration. A continuous culture with Cf PR-22 was run in the BCR using 1% alkali-pretreated sugar cane bagasse and mineral media, at dilution rates ranging from 0.04 to 0.22 1/h. The highest enzymatic productivity values were found at 0.08 1/h with 1846.4 ± 126.4 and 101.6 ± 5.6 U/L·h for xylanase and CMCase, respectively. Effluent from the BCR in steady state was transferred to an enzymatic reactor operated in fed-batch mode with an initial load of 75 g of pretreated sugar cane bagasse; saccharification was then performed in an STR at 55°C and 300 rpm for 90 h. The constant addition of fresh enzyme as well as the increase in time of contact with the substrate increased the total soluble sugar concentration 83% compared to the value obtained in a batch enzymatic reactor. This advantageous strategy may be used for industrial enzyme pretreatment and saccharification of lignocellulosic wastes to be used in bioethanol and chemicals production from lignocellulose. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:321-326, 2016.
Subject(s)
Cellulase/metabolism , Cellulomonas/enzymology , Cellulose/biosynthesis , Endo-1,4-beta Xylanases/metabolism , Saccharum/metabolism , Bioreactors , Cellulase/biosynthesis , Cellulomonas/cytology , Cellulose/chemistry , Centrifugation , Endo-1,4-beta Xylanases/biosynthesis , Fermentation , Saccharum/chemistryABSTRACT
OBJECTIVE: To obtain micro propagated Uncaria tomentosa plantlets with enhanced secondary metabolites production, long-term responses to salicylic acid (SA) pre-treatments at 1 and 100 µM were evaluated after propagation of the plantlets in a SA-free medium. RESULTS: SA pre-treatments of single node cuttings OF U. tomentosa produced long-term responses in microplants grown for 75 days in a SA-free medium. Reduction in survival rate, root formation, and stem elongation were observed only with 100 µM SA pre-treatments with respect to the control (0 + DMSO).Both pre-treatments enhanced H2O2 and inhibited superoxide dismutase and catalase activities, while guaiacol peroxidase was increased only with 1 µM SA. Also, both pre-treatments increased total monoterpenoid oxindole alkaloids by ca. 55 % (16.5 mg g(-1) DW), including isopteropodine, speciophylline, mitraphylline, isomitraphylline, rhynchopylline, and isorhynchopylline; and flavonoids by ca. 21 % (914 µg g(-1) DW), whereas phenolic compounds were increased 80 % (599 µg g(-1) DW) at 1 µM and 8.2 % (359 µg g(-1) DW) at 100 µM SA. CONCLUSION: Pre-treatment with 1 µM SA of U.tomentosa microplants preserved the survival rate and increased oxindole alkaloids, flavonoids, and phenolic compounds in correlation with H2O2 and peroxidase activity enhancements, offering biotechnological advantages over non-treated microplants.
Subject(s)
Antioxidants/metabolism , Cat's Claw/drug effects , Salicylic Acid/metabolism , Secondary Metabolism/drug effects , Alkaloids/analysis , Cat's Claw/enzymology , Cat's Claw/growth & development , Cat's Claw/metabolism , Culture Media/chemistry , Flavonoids/analysis , Hydrogen Peroxide/analysis , Indoles/analysis , Monoterpenes/analysis , Oxindoles , Phenols/analysis , Plant Roots/growth & development , Plant Stems/growth & development , Survival AnalysisABSTRACT
This review aims to explore the needs and opportunities of research & development in the field of biowaste biorefinery in Europe. Modern industry in recent years is giving its close attention on organic waste as a new precious bioresource. Specific biowaste valorisation pathways are focusing on food processing waste, being food sector the first manufacture in Europe. Anyway they need to be further tested and validated and then transferred at the larger scale. In particular, they also need to become integrated, combining biomass pretreatments and recovery of biogenic chemicals with bioconversion processes in order to obtain a large class of chemicals. This will help to (a) use the whole biowaste, by avoiding producing residues and providing to the approach the required environmental sustainability, and (b) producing different biobased products that enter different markets, to get the possible economical sustainability of the whole biorefinery. However, the costs of the developed integrated processes might be high, mostly for the fact that the industry dealing with such issues is still underdeveloped and therefore dominated by high processing costs. Such costs can be significantly reduced by intensifying research & development on process integration and intensification. The low or no cost of starting material along with the environmental benefits coming from the concomitant biowaste disposal would offset the high capital costs for initiating such a biorefinery. As long as the oil prices tend to increase (and they will) this strategy will become even more attractive.
Subject(s)
Biotechnology/methods , Research , Waste Products/analysis , Biomass , Europe , Inventions , Renewable EnergyABSTRACT
Biohydrogen is a sustainable form of energy as it can be produced from organic waste through fermentation processes involving dark fermentation and photofermentation. Very often biohydrogen is included as a part of biorefinery approaches, which reclaim organic wastes that are abundant sources of renewable and low cost substrate that can be efficiently fermented by microorganisms. The aim of this work was to critically assess selected bioenergy alternatives from organic solid waste, such as biohydrogen and bioelectricity, to evaluate their relative advantages and disadvantages in the context of biorefineries, and ï¬nally to indicate the trends for future research and development. Biorefining is the sustainable processing of biomass into a spectrum of marketable products, which means: energy, materials, chemicals, food and feed. Dark fermentation of organic wastes could be the beach-head of complete biorefineries that generate biohydrogen as a first step and could significantly influence the future of solid waste management. Series systems show a better efficiency than one-stage process regarding substrate conversion to hydrogen and bioenergy. The dark fermentation also produces fermented by-products (fatty acids and solvents), so there is an opportunity for further combining with other processes that yield more bioenergy. Photoheterotrophic fermentation is one of them: photosynthetic heterotrophs, such as non-sulfur purple bacteria, can thrive on the simple organic substances produced in dark fermentation and light, to give more H2. Effluents from photoheterotrophic fermentation and digestates can be processed in microbial fuel cells for bioelectricity production and methanogenic digestion for methane generation, thus integrating a diverse block of bioenergies. Several digestates from bioenergies could be used for bioproducts generation, such as cellulolytic enzymes and saccharification processes, leading to ethanol fermentation (another bioenergy), thus completing the inverse cascade. Finally, biohydrogen, biomethane and bioelectricity could contribute to significant improvements for solid organic waste management in agricultural regions, as well as in urban areas.
Subject(s)
Bioelectric Energy Sources , Biofuels/analysis , Solid Waste/analysis , Waste Management , Fermentation , Hydrogen/analysis , Methane/analysisABSTRACT
The catalytic fraction of the Cellulomonas flavigena PN-120 oligomeric ß-glucosidase (BGLA) was expressed both intra- and extracellularly in a recombinant diploid of Saccharomyces cerevisiae, under limited nutrient conditions. The recombinant enzyme (BGLA¹5) expressed in the supernatant of a rich medium showed 582 IU/L and 99.4 IU/g dry cell, with p-nitrophenyl-ß-D-glucopyranoside as substrate. BGLA¹5 displayed activity against cello-oligosaccharides with 2-5 glucose monomers, demonstrating that the protein is not specific for cellobiose and that the oligomeric structure is not essential for ß-D-1,4-bond hydrolysis. Native ß-glucosidase is inhibited almost completely at 160 mM glucose, thus limiting cellobiose hydrolysis. At 200 mM glucose concentration, BGLA¹5 retained more than 50 % of its maximal activity, and even at 500 mM glucose concentration, more than 30 % of its activity was preserved. Due to these characteristics of BGLA¹5 activity, recombinant S. cerevisiae is able to utilize cellulosic materials (cello-oligosaccharides) to produce bioethanol.
Subject(s)
Cellulomonas/enzymology , Cellulomonas/genetics , Recombinant Proteins/metabolism , Saccharomyces cerevisiae/genetics , beta-Glucosidase/genetics , beta-Glucosidase/metabolism , Diploidy , Enzyme Activation/drug effects , Enzyme Inhibitors/pharmacology , Glucose/metabolism , Glucose/pharmacology , Hydrolysis , Oligosaccharides/metabolism , Recombinant Proteins/geneticsABSTRACT
We evaluated the production of holocellulases from the cellulolytic microorganisms Cellulomonas flavigena PR-22 and Trichoderma reesei MCG 80 using as substrates the organic fraction of municipal solid waste (OFMSW) and digestates from a hydrogenogenic-methanogenic bioenergy production process. The first set of experiments (E1) used the mutant actinobacteria C. flavigena PR-22 whereas another set (E2) used the mutant filamentous fungi T. reesei MCG 80. In E1 with OFMSW as substrate, xylanolytic activities ranged from 1800 to 3900 international units g(holocellulose)(-1) (IU g(hol)(-1)), whereas the cellulolytic activities ranged from 220 to 420 IU g(hol)(-1). The variation of agitation speed did not have a significant effect on enzyme activity, whereas the increase of substrate concentration had a significant negative effect on both xylanolytic and cellulolytic activities on a holocellulose feed basis. Regarding E2, the OFMSW was evaluated at 1, 2 and 3 % volatile solids (VS). At 2 % VS the best filter paper activities were 1200 filter paper units (FPU) l(-1); however, in a holocellulase basis the best result was 67 FPU g(hol)(-1), corresponding to 1 % VS. Next, OFMSW was compared with OFMSW supplemented with lactose, digested solids from hydrogenogenic fermentation (D1) and digested solids from a two-stage process (D2). Against expectations, no positive effect was found in OFMSW due to lactose. The best enzymatic titres were in the order D1 > OFMSW ≈ OFMSW + lactose > D2. The use of digestates from hydrogenogenic fermentation for enzyme production holds promise for waste management. It promotes energy and added-value bioproduct generation-a green alternative to common practice of management and disposal of organic wastes.
Subject(s)
Cellulase/metabolism , Cellulomonas/enzymology , Trichoderma/enzymology , FermentationABSTRACT
Hydrogen is a valuable clean energy source, and its production by biological processes is attractive and environmentally sound and friendly. In México 5 million tons/yr of agroindustrial wastes are generated; these residues are rich in fermentable organic matter that can be used for hydrogen production. On the other hand, batch, intermittently vented, solid substrate fermentation of organic waste has attracted interest in the last 10 years. Thus the objective of our work was to determine the effect of initial total solids content and initial pH on H2 production in batch fermentation of a substrate that consisted of a mixture of sugarcane bagasse, pineapple peelings, and waste activated sludge. The experiment was a response surface based on 2(2) factorial with central and axial points with initial TS (15-35%) and initial pH (6.5-7.5) as factors. Fermentation was carried out at 35 °C, with intermittent venting of minireactors and periodic flushing with inert N2 gas. Up to 5 cycles of H2 production were observed; the best treatment in our work showed cumulative H2 productions (ca. 3 mmol H2/gds) with 18% and 6.65 initial TS and pH, respectively. There was a significant effect of TS on production of hydrogen, the latter decreased with initial TS increase from 18% onwards. Cumulative H2 productions achieved in this work were higher than those reported for organic fraction of municipal solid waste (OFMSW) and mixtures of OFMSW and fruit peels waste from fruit juice industry, using the same process. Specific energetic potential due to H2 in our work was attractive and fell in the high side of the range of reported results in the open literature. Batch dark fermentation of agrowastes as practiced in our work could be useful for future biorefineries that generate biohydrogen as a first step and could influence the management of this type of agricultural wastes in México and other countries and regions as well.
Subject(s)
Fermentation , Hydrogen/metabolism , Industrial Waste , Agriculture , Beverages , Biofuels , Fruit , Hydrogen-Ion Concentration , Industrial Waste/analysis , Mexico , Refuse Disposal/methodsABSTRACT
The purpose of our research was to evaluate the effect of eliminating supplementation of sucrose to the reactor influent on the performance of a lab scale partially-aerated methanogenic fluidized bed bioreactor (PAM-FBBR). Two operational stages were distinguished: in the first stage the influent contained a mixture of 120/30/1000 mg/L of 2,4,6-trichlorophenol/phenol/COD-sucrose (TCP/Phe/COD-sucrose); in the second stage only the xenobiotic concentrations were the same 120/30 mg/L of TCP/Phe whereas sucrose addition was discontinued. Removal efficiencies of TCP, Phe, and COD were very high and close for both stages; i.e., η(TCP): 99.9 and 99.9%; η(Phe): 99.9 and 99.9%; η(COD) = 96.46 and 97.48% for stage 1 and stage 2, respectively. Traces of 2,4,6 dichlorophenol (0.05 mg/L) and 4-chlorophenol (0.07-0.26 mg/L) were found during the first 15 days of operation of the second stage, probably due to the adaptation to no co-substrate conditions. Net increase of chloride anion Cl(-) in effluent ranged between 59.5 and 61.5 mg Cl(-)/L that was very close to the maximum theoretical concentration of 62.8 mg Cl(-)/L. PCR-DGGE analysis revealed a richness decrease of eubacterial domain posterior to sucrose elimination from the influent whereas archaeal richness remained almost the same. However, the bioreactor performance was not negatively affected by discontinuing the addition of co-substrate sucrose. Our results indicate that the application of PAM-FBBR to the treatment of groundwaters polluted with chlorophenols and characterized by the lack of easily degradable co-substrates, is a promising alternative for on site bioremediation.
Subject(s)
Bioreactors , Chlorophenols/metabolism , Phenol/metabolism , Sucrose/metabolismABSTRACT
In the first batch solid substrate anaerobic hydrogenogenic fermentation with intermittent venting (SSAHF-IV) of the organic fraction of municipal solid waste (OFMSW), a cumulative production of 16.6 mmol H(2)/reactor was obtained. Releases of hydrogen partial pressure first by intermittent venting and afterward by flushing headspace of reactors with inert gas N(2) allowed for further hydrogen production in a second to fourth incubation cycle, with no new inoculum nor substrate nor inhibitor added. After the fourth cycle, no more H(2) could be harvested. Interestingly, accumulated hydrogen in 4 cycles was 100% higher than that produced in the first cycle alone. At the end of incubation, partial pressure of H(2) was near zero whereas high concentrations of organic acids and solvents remained in the spent solids. So, since approximate mass balances indicated that there was still a moderate amount of biodegradable matter in the spent solids we hypothesized that the organic metabolites imposed some kind of inhibition on further fermentation of digestates. Spent solids were washed to eliminate organic metabolites and they were used in a second SSAHF-IV. Two more cycles of H(2) production were obtained, with a cumulative production of ca. 2.4 mmol H(2)/mini-reactor. As a conclusion, washing of spent solids of a previous SSAHF-IV allowed for an increase of hydrogen production by 15% in a second run of SSAHF-IV, leading to the validation of our hypothesis.
Subject(s)
Fermentation , Hydrogen/metabolism , Refuse Disposal/methods , Organic Chemicals/metabolismABSTRACT
The scope of this paper encompasses the following subjects: (i) aerobic and anaerobic degradation pathways of γ-hexachlorocyclohexane (HCH); (ii) important genes and enzymes involved in the metabolic pathways of γ-HCH degradation; (iii) the instrumental methods for identifying and quantifying intermediate metabolites, such as gas chromatography coupled to mass spectrometry (GC-MS) and other techniques. It can be concluded that typical anaerobic and aerobic pathways of γ-HCH are well known for a few selected microbial strains, although less is known for anaerobic consortia where the possibility of synergism, antagonism, and mutualism can lead to more particular routes and more effective degradation of γ-HCH. Conversion and removals in the range 39%-100% and 47%-100% have been reported for aerobic and anaerobic cultures, respectively. Most common metabolites reported for aerobic degradation of lindane are γ-pentachlorocyclohexene (γ-PCCH), 2,5-dichlorobenzoquinone (DCBQ), Chlorohydroquinone (CHQ), chlorophenol, and phenol, whereas PCCH, isomers of trichlorobenzene (TCB), chlorobenzene, and benzene are the most typical metabolites found in anaerobic pathways. Enzyme and genetic characterization of the involved molecular mechanisms are in their early infancy; more work is needed to elucidate them in the future. Advances have been made on identification of enzymes of Sphingomonas paucimobilis where the gene LinB codifies for the enzyme haloalkane dehalogenase that acts on 1,3,4,6-tetrachloro 1,4-cyclohexadiene, thus debottlenecking the pathway. Other more common enzymes such as phenol hydroxylase, catechol 1,2-dioxygenase, catechol 2,3-dioxygenase are also involved since they attack intermediate metabolites of lindane such as catechol and less substituted chlorophenols. Chromatography coupled to mass spectrometric detector, especially GC-MS, is the most used technique for resolving for γ-HCH metabolites, although there is an increased participation of HPLC-MS methods. Scintillation methods are very useful to assess final degradation of γ-HCH.
Subject(s)
Biodegradation, Environmental , Enzymes/metabolism , Hexachlorocyclohexane/metabolism , Anaerobiosis , Cyclohexenes/metabolism , Gas Chromatography-Mass Spectrometry , Hexachlorocyclohexane/analysis , Hydrolases/metabolism , Sphingomonas/enzymology , Sphingomonas/geneticsABSTRACT
Mexican distilleries produce near eight million liters of mezcal per year, and generate about 90 million liters of mezcal vinasses (MV). This acidic liquid waste is very aggressive to the environment because of its high content of toxic and recalcitrant organic matter. As a result, treatment is necessary before discharge to water bodies. It is interesting, yet disturbing; verify that there is a significant gap on the treatment of MV. However, there is an abundant body of research on treatment of other recalcitrant toxic effluents that bear some similarity to MV, for example, wine vinasse, vinasses from the sugar industry, olive oil, and industrial pulp and paper wastewaters. The objective of this review is to critically organize the treatment alternatives of MV, assess their relative advantages and disadvantages, and finally detect the trends for future research and development. Experience with treatment of this set of residuals, indicates the following trends: (i) anaerobic digestion, complemented by oxidative chemical treatments (e.g. ozonation) are usually placed as pretreatments, (ii) aerobic treatment alone and combined with ozone which have been directed to remove phenolic compounds and color have been successfully applied, (iii) physico-chemical treatments such as Fenton, electro-oxidation, oxidants and so on., which are now mostly at lab scale stage, have demonstrated a significant removal of recalcitrant organic compounds, (iv) fungal pretreatment with chemical treatment followed by oxidative (O(3)) or anaerobic digestion, this combination seems to give attractive results, (v) vinasses can be co-composted with solid organic wastes, particularly with those from agricultural activities and agro-industies; in addition to soil amenders with fertilizing value to improve soil quality in typical arid lands where agave is cultivated, it seems to be a low cost technology very well suited for rural regions in underdeveloped countries where more sophisticated technologies are difficult to adopt, due to high costs and requirements of skilled personnel.