Bioprocessing of Two Crop Residues for Animal Feeding into a High-Yield Lovastatin Feed Supplement.

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.

Biohydrogen, biomethane and bioelectricity as crucial components of biorefinery of organic wastes: a review.

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 finally 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.

The influence of total solids content and initial pH on batch biohydrogen production by solid substrate fermentation of agroindustrial wastes.

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.

Influence of discontinuing feeding degradable cosubstrate on the performance of a fluidized bed bioreactor treating a mixture of trichlorophenol and phenol.

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.

Enzymes involved in the biodegradation of hexachlorocyclohexane: a mini review.

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.

Treatment of mezcal vinasses: a review.

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.

Re-fermentation of washed spent solids from batch hydrogenogenic fermentation for additional production of biohydrogen from the organic fraction of municipal solid waste.

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.

Una generalización del modelo de reacciones en serie y paralelo serie para reactores de mezcla completa / A generalization of the series and parallel-series reaction model for complete mix reactors

Este trabajo se organiza alrededor de cinco lemas. En los tres primeros lemas se generalizó el modelo de reacciones de primer orden consecutivas en serie en un reactor de mezcla completa en fase líquida y se obtuvo soluciones algebraicas para las concentraciones normalizadas del compuesto madre, especies intermedias, y compuesto producto final para un esquema de "p" pasos y p+ 1 especies. También se demostró que solamente existen soluciones algebraicas para la concentración máxima de la especie A2 y el tiempo de retención en que dicha concentración es alcanzada tA2,max. En los dos últimos lemas se desarrolló ecuaciones generales para las concentraciones normalizadas de reactivo, compuestos intermediarios y producto final del modelo paralelo-serie generalizado de reacciones de primer orden de dos ramas y "p" pasos en cada rama para un reactor de mezcla completa. Finalmente, se simuló la decloración reductiva de PCE de cuatro pasos y cinco especies químicas (reacciones en serie) utilizando uno de los modelos determinados aquí, así como la decloración reductiva del 2,4,6-triclorofenol (TCF) (arreglo en paralelo serie de dos ramas paralelas y 4 especies por rama) y sus intermediarios. Ambas simulaciones predijeron razonablemente bien las concentraciones de PCE y TCF, así como sus respectivos compuestos intermediarios para casos reportados en la literatura.

Hydrogen generation via anaerobic fermentation of paper mill wastes.

The objective of this work was to determine the hydrogen production from paper mill wastes using microbial consortia of solid substrate anaerobic digesters. Inocula from mesophilic, continuous solid substrate anaerobic digestion (SSAD) reactors were transferred to small lab scale, batch reactors. Milled paper (used as a surrogate paper waste) was added as substrate and acetylene or 2-bromoethanesulfonate (BES) was spiked for methanogenesis inhibition. In the first phase of experiments it was found that acetylene at 1% v/v in the headspace was as effective as BES in inhibiting methanogenic activity. Hydrogen gas accumulated in the headspace of the bottles, reaching a plateau. Similar final hydrogen concentrations were obtained for reactors spiked with acetylene and BES. In the second phase of tests the headspace of the batch reactors was flushed with nitrogen gas after the first plateau of hydrogen was reached, and subsequently incubated, with no further addition of inhibitor nor substrate. It was found that hydrogen production resumed and reached a second plateau, although somewhat lower than the first one. This procedure was repeated a third time and an additional amount of hydrogen was obtained. The plateaux and initial rates of hydrogen accumulation decreased in each subsequent incubation cycle. The total cumulative hydrogen harvested in the three cycles was much higher (approx. double) than in the first cycle alone. We coined this procedure as IV-SSAH (intermittently vented solid substrate anaerobic hydrogen generation). Our results point out to a feasible strategy for obtaining higher hydrogen yields from the fermentation of industrial solid wastes, and a possible combination of waste treatment processes consisting of a first stage IV-SSAH followed by a second SSAD stage. Useful products of this approach would be hydrogen, organic acids or methane, and anaerobic digestates that could be used as soil amenders after post-treatment.

A side-by-side comparison of two systems of sequencing coupled reactors for anaerobic digestion of the organic fraction of municipal solid waste.

The objective of this work was to compare the performance of two laboratory-scale, mesophilic systems aiming at the anaerobic digestion of the organic fraction of municipal solid wastes (OFMSW). The first system consisted of two coupled reactors packed with OFMSW (PBR1.1-PBR1.2) and the second system consisted of an upflow anaerobic sludge bed reactor (UASB) coupled to a packed reactor (UASB2.1-PBR2.2). For the start-up phase, both reactors PBR 1.1 and the UASB 2.1 (also called leading reactors) were inoculated with a mixture of non-anaerobic inocula and worked with leachate and effluent full recirculation, respectively. Once a full methanogenic regime was achieved in the leading reactors, their effluents were fed to the fresh-packed reactors PBR1.2 and PBR2.2, respectively. The leading PBR 1.1 reached its full methanogenic regime after 118 days (Tm, time to achieve methanogenesis) whereas the other leading UASB 2.1 reactor reached its full methanogenesis regime after only 34 days. After coupling the leading reactors to the corresponding packed reactors, it was found that both coupled anaerobic systems showed similar performances regarding the degradation of the OFMSW. Removal efficiencies of volatile solids and cellulose and the methane pseudo-yield were 85.95%, 80.88% and 0.109 NL CH4 g(-1) VS(fed) in the PBR-PBR system; and 88.75%, 82.61% and 0.115 NL CH4 g(-1) VS(fed0 in the UASB-PBR system [NL, normalized litre (273 degrees K, 1 ata basis)]. Yet, the second system UASB-PBR system showed a faster overall start-up.

Slaughterhouse wastewater treatment in a full-scale system with constructed wetlands.

This work evaluated the performance of a full-scale system with wetlands for slaughterhouse (abattoir) effluent treatment in the State of Hidalgo, México. The treatment system consisted of a primary sedimentation tank, an anaerobic lagoon, and a constructed subsurface-flow wetland, in series. The wetland accounted for almost 30% of the removal of organic matter. In general, the treatment system achieved satisfactory pollutant removals, but the final effluent could not meet the Mexican environmental regulations for fecal coliform counts, five-day biochemical oxygen demand (BOD5), and total suspended solids (TSS). Overall, removal levels were 91%, 89%, and 85% for BOD5, chemical oxygen demand, and TSS, respectively. However, BOD5 in the final effluent (137 mg/L) was higher than the maximum level of 30 mg/L allowed by the regulatory agency. Although organic nitrogen removal levels were approximately 80%, the nitrogen persisted in oxidation state -3 as ammonia-nitrogen, the removal of which was only 9% in the wetland stage. On average, phosphorus removal was null, and, on occasion, the phosphorus concentration in the treated effluent was higher than that of the influent. Coliform reductions in the overall system were high (on the order of 5 logs on average), whereas the coliform removal in the wetland was between 2 to 3.5 logs. The treatment system was also effective at removing pathogens (Vibrio cholerae, Salmonella, and Shigella). Further laboratory tests with the wetland effluent suggest that post treatment in a sand filter stage followed by disinfection with sodium hypochlorite (NaOCl) could help meet the Mexican discharge regulations, particularly the criteria for coliforms and total BOD5.

Comparación de dos sistemas anaerobios acoplados para la biometanización de la fracción orgánica de residuos sólidos urbanos / Comparison of two anaerobic coupled systems for biomethanization of the organic fraction of municipal solid wastes

Se comparó dos sistemas de digestión de la fracción orgánica de los residuos sólidos urbanos (FORSU), empleando dos sistemas a escala laboratorio, uno con dos reactores empacados acoplados (RE-RE) y el otro con un reactor anaerobio de manto de lodos acoplado a un reactor empacado (RANMAL-RE), todos operados en régimen mesofílico. Para la fase de arranque del RE iniciador (RE 1.1) del sistema RE-RE, y del RANMAL iniciador (RANMAL 2.1) se inoculó mezcla de inóculos no anaerobios. Alcanzado el tiempo de metanogénesis franca (TMF) en los iniciadores, sus efluentes fueron recirculados a los correspondientes RE frescos (RE 1.2 y RE 2.2) y los lixiviados procedentes de éstos se recircularon a su vez a los indicadores metanogénicos (RE 1.1 y RANMAL 2.1). La fase de arranque de RE 1.1 se hizo con recirculación continua del lixiviado hasta llegar al tiempo de metanogénesis en 118 días; el lixiviado obtenido tuvo pH 7,05; factor alfa 0,35; ácidos orgánicos volátiles (AOV) 1405 mg/l Hac; DQO de recirculación 3080mg/l; y 62.02 por ciento de metano en el biogás. Para RANMAL 2.1, el arranque inició con circulación de inóculo salvaje y desde el día 7 se alimentó con agua residual sintética; el TMF fue alcanzado a los 34 días y el efluente tuvo pH 7,13 alfa 0,36; AOV 1289mg/l Hac; DQO 2280mg/l; y 60,40 por ciento de metano. El acoplamiento de los sistemas se realizó conectando las salidas de RE 1.1 y RANMAL 2.1 a RE 1.2 y RE 2.2 respectivamente, empacados con FORSU nueva. Ambos sistemas anaerobios acoplados resultaron atractivos para degradación de FORSU, aunque RANMAL-RE fue más rápido en el primer arranque, removió más sólidos volátiles (SV) que RE-RE y generó más metano. Las eficiencias de remoción de metano fueron 85,95 por ciento 80,88 por ciento y 0,1091 CH/g-SV en RE-RE, y 88,75 por ciento 82,61 por ciento y 0,1151 CH/g-SV en RENMAL-RE

Irreversibilidad en el comportamiento adsortivo-desortivo de contaminantes en suelos y sedimentos: evaluación cuantitativa por medio de un coeficiente de histéresis diferencial / Irreversibility of the adsortion-desorption behaviour of pollutants in soils and sediments: quantitative evaluation by means of a differential hysteresis coefficient

Se propone un nuevo coeficiente de histéresis y se examina su utilidad para determinar el comportamiento de adsorción-desorción de contaminantes en sedimentos y suelos. Para varios contaminantes y matrices sólidas tales como sedimentos, la ruta de desorción es diferente de la adsorción. Este fenómeno es conocido como histéresis. En este trabajo se define un coeficiente de histéresis CH como la razón de la pendiente (dervada) de la curva de adsorción y la pendiente de la curva de desorción en un punto dado (Cj,qj) de interés. se demuestra que: i)CH es adimensional y cuando la histéresis no es importante, CH=1, esto es, la adsorción es reversible, mientras que cuando la histéresis es importante, CH > 1, esto es, la adsorción es irreversible; ii)el CH puede ser determinado en cualquier punto (Cj,qj) deinterés de la curva de adsorción, realizando unos pocos pasos consecutivos de desorción, no habiendo necesidad de determinar el ciclo completo de adsorción-desorción; iii)existen también ecuaciones analíticas, particulares y simples para encontar CH para los modelos de isotermas lineal, Freundlich y Langmuir; y iv)el CH muestra varias ventajas sobre los bien conocidos índices de histéresis definidos por Huang y Weber (1997) y Ma et al. (1993). Utilizando datos experimentales de la literatura arbitrada, también se demuestra que el CH es útil y provee una base cuantitativa para i)comparar la irreversibilidad de la adsorción de diferentes contaminantes individuales sobre un suelo dado; ii)comparar la irreversibilidad de la adsorción de un contaminante dado sobre suelos diferentes; iii)determinar el efecto del añejamiento y de la exposición a la intemperie sobre la irreversibilidad de la adsorción