Bacterial indicator taxa in soils under different long-term agricultural management.

AIMS: In this study, the species indicator test was used to identify key bacterial taxa affected by changes in the soil environment as a result of conservation agriculture or conventional practices. METHODS AND RESULTS: Soils cultivated with wheat (Triticum spp. L.) and maize (Zea mays L.) under different raised bed planting systems for 20 years, that is, varying crop residue and fertilizer management, were used. Taxonomic- and divergence-based 16S-metagenomics, and IndVal analysis were used to study the bacterial communities and identify indicator taxa (genus and OTU97 ) affected by agricultural practices. Although, some phyla were affected significantly by different treatments, the taxonomic assemblages at phylum level were similar. Bacterial taxa related to different processes of the N-cycle were indicators of different fertilization rates, for example, Azorhizobium, Nostoc and Nitrosomonas. A large number of OTU97 were indicators for conventionally tilled beds and their distribution was defined by soil organic carbon. IndVal analysis identified different taxa in each of the residue management systems. This suggests that although the same organic material remains in the field, crop residue management affects specific taxa. The taxa indicator of the burned residues belonged mainly to the order SBR1031 (Anaerolineae, Chloroflexi), and the genera Bacillus and Alicyclobacillus. CONCLUSIONS: N-fertilizer application rates affected N-cycling taxa. Tillage affected Actinobacteria members and organic matter decomposers. Although the same crop residue was retained in the field, organic material management was important for specific taxa. SIGNIFICANCE AND IMPACT OF THE STUDY: In this study, we report that agricultural practice affected soil bacterial communities. We also identified distinctive taxa and related their distribution to changes in the soil environment resulting from different agricultural practices.

Greenhouse gas emissions from stabilization ponds in subtropical climate.

Waste stabilization ponds (WSPs) are a cost-efficient method to treat municipal and non-toxic industrial effluents. Numerous studies have shown that WSPs are a source of greenhouse gas (GHG). However, most reports concerned anaerobic ponds (AP) and few have addressed GHG emissions from facultative (FP) and aerobic/maturation ponds (MPs). In this paper, GHG emissions from three WSP in series are presented. These WSPs were designed as anaerobic, facultative and aerobic/maturation and were treating agricultural wastewater. CH4 fluxes from 0.6 +/- 0.4 g CH4 m(-2) d(-1) in the MP, to 7.0 +/- 1.0 g CH4 m(-2) d(-1) in the (AP), were measured. A linear correlation was found between the loading rates of the ponds and CH4 emissions. Relatively low CO2 fluxes (0.2 +/- 0.1 to 1.0 +/- 0.8 g CO2 m(-2) d(-1)) were found, which suggest that carbonate/bicarbonate formation is caused by alkaline pH. A mass balance performed showed that 30% of the total chemical oxygen demand removed was converted to CH4. It has been concluded that the WSP system studied emits at least three times more GHG than aerobic activated sludge systems and that the surface loading rate is the most important design parameter for CH4 emissions.

A comparative study of Taxol production in liquid and solid-state fermentation with Nigrospora sp. a fungus isolated from Taxus globosa.

AIMS: To determine in liquid (LF) and solid-state fermentation (SSF) the effect of medium concentration on growth and Taxol produced by Nigrospora sp., a fungus isolated from the Mexican yew. METHODS AND RESULTS: Nigrospora sp. was grown at different concentrations of the base culture medium M1D, i.e. two (2×), four (4×), six (6×) and eight times (8×) the base concentration. The titres of Taxol determined by competitive inhibition enzyme immunoassay increased with increasing medium concentration in LF and SSF but were higher in SSF in every medium concentration. The Taxol produced in SSF and LF with 8× medium was 221 and 142 ng l(-1) . The SSF gave also higher biomass, growth and sugar utilization than LF in every medium. The growth and sugar consumption were modelled by the logistic and the Pirt models, respectively. However, the Luedeking-Piret model was unsuitable for Taxol. CONCLUSIONS: The SSF surpassed LF in terms of Taxol, growth and sugar utilization; thus, it has significant advantages over LF. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report on Taxol production by SSF and the first contribution to evaluate the influence of the medium on Taxol production in LF and SSF.

The bacterial community in 'taberna' a traditional beverage of Southern Mexico.

AIMS: To characterize the bacterial community of taberna, an alcoholic traditional beverage from the Southern part of Mexico produced by the fermentation of the coyol palm sap (Acrocomia aculeate). METHODS AND RESULTS: Bacterial 16S rDNA libraries were constructed from metagenomic DNA extracted during the fermentation process at 0, 60 and 108 h. A total of 154 clones were sequenced, and 13, 10 and nine unique sequences were found at each sampling time. At the onset of the fermentation, Zymomonas mobilis, Fructobacillus spp., Pantoea agglomerans and other Gammaproteobacteria were detected. After 60 h, lactic acid bacteria were found and 30% of clones in the library were related to Lactobacillus nagelii, L. sucicola and L. sp. By the end of the experiment, i.e. after 108 h, the bacterial community included Z. mobilis, Lact. nagelii and Acetobacter pasteurianus. CONCLUSIONS: Our results suggest that Z. mobilis population represented an important proportion of the bacterial community (60-80%), as well as the lactobacilli during the fermentation process. The bacterial diversity was low and decreased as the fermentation progressed. SIGNIFICANCE AND IMPACT OF THE STUDY: This culture-independent study suggests that Z. mobilis and lactobacilli play an important role in the alcoholic fermentation of the taberna beverage.

Impact of moisture dynamic and sun light on anthracene removal from soil.

In a previous study, remediation of anthracene from soil was faster in the top 0-2 cm layer than in the lower soil layers. It was not clear whether this faster decrease was due to biotic or abiotic processes. Anthracene-contaminated soil columns were covered with black or transparent perforated polyethylene so that aeration occurred but that fluctuations in water content were minimal and light could reach (LIGHT treatment) or not reach the soil surface (DARK treatment), or left uncovered so that soil water content fluctuate and light reached the soil surface (OPEN treatment). The amount of anthracene, microbial biomass C, and microbial activity as reflected by the amount of CO(2) produced within 3 days were determined in the 0-2 cm, 2-8 cm, and 8-15 cm layer after 0, 3, 7, 14, and 28 days. In the 0-2 cm layer of the OPEN treatment, 17% anthracene remained, 48% in the LIGHT treatment and 61% in the DARK treatment after 28 days. In the 2-8 cm and 8-15 cm layer, treatment had no significant effect on the dissipation of anthracene from soil after 14 and 28 days. It was found that light and fluctuations in water content stimulated the removal of anthracene from the top 0-2 cm soil layer, but not from the lower soil layers. It can be speculated that covering contaminated soil or piling it up will inhibit the dissipation of the contaminant.

Flocculant in wastewater affects dynamics of inorganic N and accelerates removal of phenanthrene and anthracene in soil.

Recycling of municipal wastewater requires treatment with flocculants, such as polyacrylamide. It is unknown how polyacrylamide in sludge affects removal of polycyclic aromatic hydrocarbons (PAH) from soil. An alkaline-saline soil and an agricultural soil were contaminated with phenanthrene and anthracene. Sludge with or without polyacrylamide was added while emission of CO(2) and concentrations of NH(4)(+), NO(3)(-), NO(2)(-), phenanthrene and anthracene were monitored in an aerobic incubation experiment. Polyacrylamide in the sludge had no effect on the production of CO(2), but it reduced the concentration of NH(4)(+), increased the concentration of NO(3)(-) in the Acolman soil and NO(2)(-) in the Texcoco soil, and increased N mineralization compared to the soil amended with sludge without polyacrylamide. After 112d, polyacrylamide accelerated the removal of anthracene from both soils and that of phenanthrene in the Acolman soil. It was found that polyacrylamide accelerated removal of phenanthrene and anthracene from soil.

Sheep manure vermicompost supplemented with a native diazotrophic bacteria and mycorrhizas for maize cultivation.

An orthogonal experimental design L9 (3(4)) with 10 repetitions was used to investigate the effect of Glomus claroideum (0, 1 or 2g(-1) plant), G. fasciculatum (0, 1 or 2g plant(-1)), native diazotrophic bacteria (0, 10(3) and 10(5) UFC ml(-1)) and sheep manure vermicompost (0%, 5% and 10% v/v) on maize plant growth, N and P in leaves and mycorrhization percent. Vermicompost explained most of the variation found for leaf number, wet weight, stem height, and diameter. Both mycorrhizas increased the plant wet weight but G. fasciculatum the most. Mycorrhization increased the P content, but not the N content. Mycorrhizal colonization increased when diazotrophic bacteria and vermicompost were added. It was found that weight of maize plants cultivated in peat moss amended with vermicompost increased when supplemented with G. fasciculatum and diazotrophic bacteria.

Remediation of PAHs in a saline-alkaline soil amended with wastewater sludge and the effect on dynamics of C and N.

Contamination of soil with hydrocarbons occurs frequently and organic material, such as sludge, is often applied to accelerate their dissipation. Little is known, however, how sludge characteristics affect removal of polycyclic aromatic hydrocarbons (PAHs) from alkaline-saline soil. Soil of the former lake Texcoco with pH 9 and electrolytic conductivity 7 dS m(-1) was contaminated with phenanthrene and anthracene and amended with sludge, sterilized sludge, sludge adjusted to maintain pH in contaminated soil or glucose plus an inorganic N and P source while emission of CO2 and concentrations of NH4+, NO3-, NO2-, extractable P, phenanthrene and anthracene were monitored in an aerobic incubation experiment of 112 days. An agricultural soil from Acolman treated in the same way served as control. Contaminating the Texcoco soil increased emission of CO2 significantly, but not in the Acolman soil. After 112 days, the largest concentration of anthracene and phenanthrene was found in the Acolman soil added with glucose and the lowest in the sludge-amended soil. The largest concentration of anthracene in the Texcoco soil was found in soil added with sterile sludge and the lowest in the sludge-amended soil. The largest concentration of phenanthrene in the Texcoco soil was found in the glucose-amended soil and the lowest in the sludge-amended soil. It was found that addition of sludge removed more phenanthrene, but not anthracene from soil compared to the unamended contaminated soil, glucose inhibited dissipation of PAHs while microorganisms in the sludge contributed to their removal, and adjustment of soil pH had no effect. Organic material can be used to accelerate removal of hydrocarbons from soil, but the effect is controlled by soil type, contaminant and organic material characteristics.

Dynamics of nitrogen in a PAHs contaminated soil amended with biosolid or vermicompost in the presence of earthworms.

Nitrogen mineralization in PAHs contaminated soil in presence of Eisenia fetida amended with biosolid or vermicompost was investigated. Sterilized and unsterilized soil was contaminated with PAHs, added with E. fetida and biosolid or vermicompost and incubated aerobically for 70 days, while dynamics of inorganic N were monitored. Addition of E. fetida to sterilized soil increased concentration of NH(4)(+) 100> mg N kg(-1), while concentrations in unsterilized remained <60 mg N kg(-1) except for soil amended with biosolid plus PAHs where it increased to >80 mg kg(-1). Addition of PAHs had no significant effect on concentration of NH(4)(+) compared to the unamended soil, except in the soil added with biosolid. Addition of E. fetida to sterilized soil increased concentration of NO(2)(-) 15> mg N kg(-1) while concentrations in unsterilized soil remained <7.5 mg N kg(-1) except for soil amended with biosolid where it increased to >20 mg kg(-1). Addition of PAHs had no significant effect on concentration of NO(2)(-) compared to the unamended soil. Addition of biosolid and vermicompost increased concentration of NO(3)(-), while addition of E. fetida decreased concentration of NO(3)(-) in biosolid amended soil. It was found that NH(4)(+) and NO(2)(-) oxidizers were present in the gut of E. fetida, but their activity was not sufficient enough to inhibit a temporarily increase in concentrations of NH(4)(+) and NO(2)(-). Contamination with PAHs induced immobilization of N in biosolid or vermicompost amended soil, as did feeding of E. fetida on biosolid or vermicompost.

Dynamics of carbon and nitrogen in a mixture of polycyclic aromatic hydrocarbons contaminated soil amended with organic residues.

Contamination of soil with polycyclic aromatic hydrocarbons (PAHs) through oil spills occurs frequently in Mexico. PAHs are highly resistant to degradation and restoration of these contaminated soils might be achieved by applying readily available organic material. A clayey soil was contaminated in the laboratory with different forms of PAHs, i.e. phenanthrene, anthracene and benzo(a)pyrene, and amended with maize or biosolids while production of carbon dioxide (CO2), dynamics of ammonia (NH4-), nitrate (NO3-) and PAHs were monitored. The largest CO2 production rate was found in soil added with maize and biosolids and the lowest in the unamended soil. The concentration of PAHs added to the sterilized soil did not change significantly over time and addition of organic material had no significant effect on it. The concentration of PAHs in unsterilized soil decreased sharply in the first weeks independent of addition of organic material and changes were small thereafter. After 100 days, 77% of benzo(a)pyrene was removed from soil, but 91% and 93% of phenanthrene and anthracene, respectively was removed. It was concluded that the autochthonous microbial population degraded phenanthrene, anthracene and benzo(a)pyrene, but neither biosolids nor maize accelerated the decomposition of PAHs or affected their residual concentration.

Dynamics of C, N and P in soil amended with biosolids from a pharmaceutical industry producing cephalosporines or third generation antibiotics: a laboratory study.

Large parts of the central highlands of Mexico are heavily eroded and the success of a planned reforestation program will greatly improve when the organic matter and nutrient content of the soil increases prior to the planting of the trees. This study investigated how the application of biosolids from a pharmaceutical company producing cephalosporines or third generation antibiotics could be used as a soil amendment and affect dynamics of C, P and N in soil. A sandy clay loam soil was sampled, amended with 24 g of dry biosolids kg(-1) dry soil or approximately 32 x 10(3) kg ha(-1) for the 0-10 cm layer, and incubated aerobically while production of carbon dioxide (CO(2)), dynamics of ammonium (NH(4)(+)),nitrite (NO(2)(-)), nitrate (NO(3)(-)), sodium bicarbonate (NaHCO(3)) extractable phosphorus (PO(4)(3-)), and microbial biomass carbon (C) were monitored. Results showed that the biosolid with pH 12, organic C content 162 g kg(-1), total N 21 g kg(-1), was of excellent quality considering its heavy metal content (USEPA) and a class "B" (USEPA) biosolid considering the amount of pathogens. No cephalosporines could be detected in the biosolid. Addition of biosolid to soil increased production of CO(2) 1.4 times and added >60 mg NH(4)(+) kg(-1). The application of biosolids did not significantly increase the concentration of NO(2)(-) which remained <2 mg N kg(-1) soil, but the concentration of NO(3)(-) did increase with 175 mg N kg(-1) soil. The microbial biomass C did not change when sewage biosolids was added and concentrations of extractable PO(4)(3-) only increased temporarily. Washing the biosolids reduced concentrations of NH(4)(+) and NO(3)(-), but also reduced pathogens and concentrations of chloride (Cl(-)), which might pose a treat to humans and the environment, respectively. Although the biosolid added valuable nutrients to the soil and did not inhibit C and N mineralization, further investigation into possible long-term environmental effects on soil processes and plant growth is necessary before this biosolid can be used in the field.

Bioremediation of polycyclic aromatic hydrocarbon-contaminated saline-alkaline soils of the former Lake Texcoco.

Polycyclic aromatic hydrocarbons (PAHs) such as phenanthrene, anthracene and Benzo[a]pyrene (BaP) are toxic for the environment. Removing these components from soil is difficult as they are resistant to degradation and more so in soils with high pH and large salt concentrations as in soil of the former lake Texcoco, but stimulating soil micro-organisms growth by adding nutrients might accelerate soil restoration. Soil of Texcoco and an agricultural Acolman soil, which served as a control, were spiked with phenanthrene, anthracene and BaP, added with or without biosolid or inorganic fertilizer (N, P), and dynamics of PAHs, N and P were monitored in a 112-day incubation. Concentrations of phenanthrene did not change significantly in sterilized Acolman soil, but decreased 2-times in unsterilized soil and >25-times in soil amended with biosolid and NP. The concentration of phenanthrene in unsterilized soil of Texcoco was 1.3-times lower compared to the sterilized soil, 1.7-times in soil amended with NP and 2.9-times in soil amended with biosolid. In unsterilized Acolman soil, degradation of BaP was faster in soil amended with biosolid than in unamended soil and soil amended with NP. In unsterilized soil of Texcoco, degradation of BaP was similar in soil amended with biosolid and NP but faster than in the unamended soil. It was found that application of biosolid and NP increased degradation of phenanthrene, anthracene and BaP, but to a different degree in alkaline-saline soil of Texcoco compared to an agricultural Acolman soil.

Dissipation of polycyclic aromatic hydrocarbons from soil added with manure or vermicompost.

The dissipation of three PAHs, i.e., 500 mg phenanthrene kg(-1) soil, 350 mg anthracene kg(-1) soil and 150 mg benzo(a)pyrene kg(-1) soil, was investigated in soil from Acolman (México) added with cow manure or vermicompost while production of CO(2) and inorganic N was monitored. At day 0, recovery of added phenanthrene was 95%, anthracene 96% and benzo(a)pyrene 100% in sterilized soil and concentrations did not change significantly in sterilized soil over time. Application of organic material did not affect the concentration of phenanthrene and anthracene, which decreased sharply in the unsterilized soil in the first weeks of the incubation. Less than 3% of the added phenanthrene was detected after 100 days and less than 8.5% of the added anthracene (mean of the two experiments). The decrease in concentration of benzo(a)pyrene (BaP) was not fast as that of phenathrene and anthracene, and 22% was extractable from soil still after 100days. It was concluded that addition of farm yard manure (FYM) and vermicompost only had an effect on the initial dissipation of phenanthrene, anthracene and benzo(a)pyrene in soil of Acolman.

Utilization of vinasses as soil amendment: consequences and perspectives.

Vinasses are a residual liquid generated after the production of beverages, such as mezcal and tequila, from agave (Agave L.), sugarcane (Saccharum officinarum L.) or sugar beet (Beta vulgaris L.). These effluents have specific characteristics such as an acidic pH (from 3.9 to 5.1), a high chemical oxygen demand (50,000-95,000 mg L(-1)) and biological oxygen demand content (18,900-78,300 mg L(-1)), a high total solids content (79,000 and 37,500 mg L(-1)), high total volatile solids 79,000 and 82,222 mg L(-1), and K(+) (10-345 g L(-1)) content. Vinasses are most commonly discarded onto soil. Irrigation of soil with vinasses, however, may induce physical, chemical and biochemical changes and affect crop yields. Emission of greenhouse gases (GHG), such as carbon dioxide, nitrous oxide and methane, might increase from soils irrigated with vinasses. An estimation of GHG emission from soil irrigated with vinasses is given and discussed in this review.

Poultry slaughter wastewater treatment with an up-flow anaerobic sludge blanket (UASB) reactor.

Removal of organic material from poultry slaughter wastewater as determined by changes in biological oxygen demand (BOD5) was investigated by adding three different types of inoculum combining cow manure, yeast extract or hydraulic residence time as variables with response vector of reduction of BOD5. In a 3-l reactors, a 95% removal of BOD5 from poultry slaughter wastewater was obtained with organic loading rates up to 31 kg BOD5 m(-3) d(-1) without loss of stability. This 95% removal was obtained between 25 and 39 degrees C with a hydraulic residence time between 3.5 and 4.5 h. The growth of the consortium of micro-organisms in the reactor followed a first-order kinetic with a constant specific growth rate of 0.054 h(-1). It was concluded that an inoculum from cow manure added with nutrients and yeast extract allowed a 95% removal of BOD5 from poultry slaughter wastewater at ambient temperatures within a hydraulic residence time of 4 h, sharply reducing possible environmental hazards.

Optimization of gibberellic acid production by immobilized Gibberella fujikuroi mycelium in fluidized bioreactors.

An orthogonal experimental design L9 (3(4)) was used to investigate effects of temperature, pH, C:N ratio (glucose-C, NH4Cl-N) and concentrations of rice flour on production of gibberellic acid by Gibberella fujikuroi in 3.5 l fluidized bioreactors. The gibberellic acid production in a fluidized bioreactor could reach 3.90 g l(-1), more than 3-times greater than previously reported for submerged and solid fermentations. pH, rice flour concentration and C:N ratio were the factors that most influenced the production of gibberellic acid; pH being the most important. The response surface of gibberellic acid production to changes in pH and C:N ratio or rice flour concentration indicated that greatest production was found with a C:N ratio of 36.8 and pH 5 while the optimum concentration for rice flour was 2 g l(-1) and production increased with increased pH. The effect of temperature on the production of gibberellic acid was also significant and greatest production was at 30 degrees C.

A method to evaluate the isothermal effectiveness factor for dynamic oxygen into mycelial pellets in submerged cultures.

Several models have been developed simulating O2 transfer in bioreactors, but three limitations are often found: (i) an inadequate kinetic representation of O2 consumption or wrong boundary conditions, (ii) unrealistic parameter values, and (iii) inadequate experimental systems. In our study we minimized those possible sources of error. Oxygen uptake rate, void fraction of the pellet, and external O2 mass transfer coefficient were experimentally obtained from bioreactor studies in which pellets of Gibberella fujikuroi were naturally formed. Michaelis-Menten kinetics and diffusion equations were used to describe the O2 consumption rate and to evaluate the effectiveness factor in dynamic mode. The nonlinear mathematical model proposed was solved by the orthogonal collocation technique. The O2 consumption rate in pellets of G. fujikuroi of 1.7-2.0 mm is only marginally inhibited by diffusion constraints under conditions tested. Simulation analysis showed that the effectiveness factor decreased as the Thiele modulus and pellet diameter increased. The proposed model was applied to experimental data reported for other fungal pellets and allowed to predict optimal conditions for O2 transfer into mycelial pellets.

Nitrogen, carbon and phosphorus mineralization in soils from semi-arid highlands of central Mexico amended with tannery sludge.

Tannery sludge contains valuable nutrients and could be used as a fertilizer to pioneering vegetation in heavily eroded soils of the semi-arid highlands of central Mexico. Soil collected under and outside the canopy of mesquite (Prosopis laeviginata), huizache (Acacia tortuoso) and catclaw (Mimosa biuncifera), and cultivated with maize (Zea mays) and beans (Phaesolus vulgaris) was amended with 1.5 g tannery sludge kg-1 soil or 210 kg dry sludge ha-1 or left unamended. Amended and unamended soils were incubated aerobically for 70 days at 22 +/- 2 degrees C and CO2 production, available P, and inorganic N concentrations were monitored. The CO2 production rate, total C and P, available P, biomass C and P were larger under the canopy of the vegetation than outside of the canopy. The soils were depleted of N as more than 50 mg N kg-1 soil could not be accounted for in the first days of the incubation. Nitrification showed a lag, which lasted 28 days, and concentration of available P remained constant or increased slightly. Application of tannery sludge to soil increased CO2 production with 6.5 mg CO2 kg-1 soil d-1 and inorganic N with 30 mg N kg-1 soil after 70 days, but available P did not increase. Application of tannery sludge increased C and N mineralization and could thus provide valuable nutrients to a pioneer vegetation. Although no inhibitory effects on the biological functioning of the soil were found, further investigation into possible long-term environmental effects are necessary.

Characteristics, and carbon and nitrogen dynamics in soil irrigated with wastewater for different lengths of time.

Irrigation of agricultural land with wastewater will increase crop production, but also heavy metal concentrations and the rate of infection of farmers with pathogens. The risks associated with the use of wastewater are reduced by treating the wastewater, but treatment also reduces organic material, phosphorus and inorganic N for crops. We investigated characteristics, e.g. heavy metal concentrations, of soils of the valley of the Mezquital (Mexico) irrigated with waste from Mexico City water since 1912, 1925, 1965, 1976, 1996 or 1997, or not irrigated at all, and dynamics of C and N when soil was amended with wastewater or drainage water. Concentrations of total Mg, Hg, Mo, Ca, Cu and Cr, available concentrations of Pb, Cd and Cu increased significantly with length of irrigation (P < 0.05), but were not at hazardous concentrations. Although organic C, total N, microbial biomass C and N, and microbial activity, as witnessed by CO2 production, increased with length of irrigation, N mineralization did not. Oxidation of NO2- was inhibited and could be due to increases in salinity, toxic compounds or heavy metals. We found that N mineralization was low or absent so it will not compensate for the loss of N when the wastewater is treated and application of N fertilizer will be required to maintain the same level of crop production. The characteristics of the soils appear not to have deteriorated after years of application of wastewater, but further irrigation even with treated wastewater might increase sodicity and salinity and pose a threat to future crop production.

Characterization of five agricultural by-products as potential biofilter carriers.

Biofiltration is the most commonly used biological gas treatment technology and is extensively used for the treatment of polluted air with gas flow rates of up to 2 x 10(5) m(3)/h. It involves a filter bed of organic matter serving both as carrier for microorganisms and as nutrient supplier. Polluted gas passes through the filter bed and is cleaned by biological activity. Biofiltration is not being developed in Latin America as in the USA, Canada or Europe; the main reason probably being the absence of specific technology and of potential organic carriers locally available. Five different agriculture by-products available in Latin America: peanut shells, rice husk, coconut shells, cane bagasse and maize stubble, were chemically, physically and structurally characterized for their potential use as biofilter carrier. It was found that peanut shells could be used as biofilter carrier and therefore would have potential biological application.