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This work reports the effect of four different physicochemical pretreatments (acidic, thermal, acidic-thermal, and thermal-acidic) on an anaerobic inoculum aiming at alcohols production, using acetate and butyrate as carbon sources and hydrogen as co-substrate. Pretreatments were carried out to select microbial communities more able to use hydrogen to metabolize volatile fatty acids into their respective alcohols. Experiments were conducted in single batches using acetate and butyrate as substrates at 30 °C and with a pressurized headspace of pure H2 at 2.15 atm (218.2 MPa). Thermal and acidic-thermal pretreatments lead to higher production of both ethanol and butanol, indicating that these pretreatments successfully selected communities more suitable for acetate and butyrate solventogenesis. Kinetics modelling shows that the highest attainable concentrations of ethanol and butanol produced were 122 mg L−1 and 97 mg L−1 for the thermal pretreatment (after 17.5 days) and 87 mg L−1 and 143 mg L−1 for the acidic-thermal pretreatment (after 18.9 days). Process thermodynamics indicated that high H2 partial pressure favoured solventogenic metabolic pathways. Sequencing data showed that both thermal and acidic-thermal pretreatments selected mainly the bacterial genera Pseudomonas, Brevundimonas, and Clostridium. Acidic-thermal pretreatment selected a bacterial community more adapted to the conversion of acetate and butyrate into ethanol and butanol, respectively. Thermal-acidic pretreatment was unstable, showing significant variability between replicates. Acidic pretreatment showed the lowest alcohol production. [ABSTRACT FROM AUTHOR]

The continuous multiple tube reactor (CMTR) has been developed as a promising technology to maximize biohydrogen production (BHP) by dark fermentation (DF) by preventing excess biomass accumulation, leading to suboptimum values of specific organic loading rates (SOLR). However, previous experiences failed to achieve stable and continuous BHP in this reactor, as the low biomass retention capacity in the tube region limited controlling the SOLR. This study goes beyond the evaluation of the CMTR for DF by inserting grooves in the inner wall of the tubes to ensure better cell attachment. The CMTR was monitored in 4 assays at 25ºC using sucrose-based synthetic effluent. The hydraulic retention time (HRT) was fixed at 2 h, while the COD varied between 2–8 g L−1 to obtain organic loading rates in the 24 – 96 g COD L−1 d−1. Long-term (90 d) BHP was successfully attained in all conditions due to the improved biomass retention capacity. Optimal values for the SOLR (4.9 g COD g−1 VSS d−1) were observed when applying up to 48 g COD L−1 d−1, in which BHP was maximized. These patterns indicate a favorable balance between biomass retention and washout was naturally achieved. The CMTR looks promising for continuous BHP and is exempt from additional biomass discharge strategies. [ABSTRACT FROM AUTHOR]

The effects of toxic substance in soil matrices are evaluated by assessing adult worm survival and reproduction. Throughout the test, hundreds of juvenile potworms can be found. The current method for Enchytraeus crypticus quantification in soil samples is a laborious and time-consuming procedure that involves manual counting. The present work proposes a method for quick and reliable counting of E. crypticus by using an automated image analysis algorithm applied to soil images. Comparisons between automated and manual methods conducted in double-blind trials involving a large, routine batch of tropical artificial soil samples revealed no statistically significant differences for a wide range of worm densities. The proposed method overcomes time-consuming counts in manual methods and is suited to be deployed routinely for soil toxicity studies involving large batches of samples. [ABSTRACT FROM AUTHOR]

Hydrogen is a renewable fuel that can be biologically produced by green algae in closed anaerobic photobioreactors with light and organic carbon as energy sources. This research aimed to investigate the influence of sulfur concentration and light intensity on hydrogen and ethanol production, as well as on nutrient removal by Chlamydomonas reinhardtii (CC425) in batch cultures. The strain was cultivated in two phases: in the first step, the cultures were maintained under aerobic conditions to obtain biomass; in the second step, the biomass was transferred to closed anaerobic photobioreactors for gas generation under continuous illumination. A factorial design was accomplished to improve the biomass production in the first step, with light variation, pH, and glucose addition. Afterward, light intensity and sulfur concentration were varied to test hydrogen production in the second step. The best hydrogen production occurred in photobioreactors without sulfur addition (average increase of 7 times in the production) and under higher light intensity the productivity was 37% higher than lower light intensity (39.64 ± 2.44 µmol H2 L−1 h−1). There was an effect of sulfur concentration in the ethanol production and under higher light intensity the production was higher (203.20 ± 31.49 mg L−1). Furthermore, under conditions with the presence of sulfur, there was greater removal of ammoniacal nitrogen (5.3%), phosphate (85.0%), COD (9.1%) and acetic acid (97.2%). This research demonstrates the efficient production of hydrogen by C. reinhardtii and it shows that the process can be associated with ethanol production and nutrient removal. [ABSTRACT FROM AUTHOR]

The growing concern on the fate of toxic and persistent micropollutants in aquatic ecosystems led to the need to comprehend how these substances can be converted into less harmful chemicals. Tetrabromobisphenol A (TBBPA) is the most used brominated flame retardant (BFR) worldwide and is often detected in water bodies and wastewaters. In the past 20 years, the degradation of TBBPA has been investigated in bioreactors with different microbial communities and under a variety of operational parameters. Comprehending TBBPA biodegradation contributes to a better understanding of other flame retardants environmental fate and the optimization of wastewater treatment biotechnologies. Even though many process-optimization procedures and investigations on mixed and isolated strain functions have been conducted, understanding metabolic processes on this micropollutant breakdown remains uncovered, especially in environmental settings. Different findings on how to optimize TBBPA bioconversion and the factors influencing cometabolic and metabolic reactions may mislead further studies or suggest arguable directions. For this reason, this review summarizes and critically discusses how the main environmental and operational parameters affect TBBPA biodegradation, the main degradation pathways and subproducts, and the microorganisms and enzymatic activities involved in this process, raising some questions that should be addressed in more in-depth studies. [ABSTRACT FROM AUTHOR]

Soil toxicity tests are commonly applied using Enchytraeus crypticus to analyze reproductive outputs. However, the traditional method for counting potworms takes a long time due to the significant number of offspring. This paper compares the conventional total counting of E. crypticus juveniles (M1) and an alternative methodology (M2). The proposed methodology (M2) uses a simple random counting method (1/4) for the partial counting of juveniles and total estimation. Chronic bioassays (21 days of exposure) were performed in tropical artificial soil (TAS) using sugarcane vinasse as a hazardous substance. Comparing the final density of juveniles recorded in M1 and M2, no statistical differences were pointed out in either one. Applying analyses based on effective concentration (EC10 and EC50), no statistical differences were identified there either. The t-test showed that there was no statistical difference between the counting methods (M1 and M2) in each treatment (control and dilutions). Moreover, we ran the Tukey test for M1 and M2 methods separately and observed that 100 % of the vinasse showed a statistical difference compared to the control treatment in both (p ≤ 0.05), affirming that independent of the counting method, the ecotoxicological outputs were similar. Therefore, the proposed alternative is a suitable method for bioassay using. E. crypticus in tropical artificial soil, decreasing to 1/4 the total time required for counting. [ABSTRACT FROM AUTHOR]

The high temperature in which sugarcane vinasse (SV) is generated (~ 90 °C) and the positive effect of higher temperatures in biochemical reactions have motivated the evaluation of SV anaerobic digestion (AD) under extreme temperature conditions. Two-stage (acidogenic/methanogenic) and single-stage (methanogenic) AD of SV were evaluated under 70 °C in structured-bed reactors. The extreme temperature was beneficial to the acidogenic step of the two-stage AD process. The methane production, however, was hindered at 70 °C. The VMP of the single and two-stage reactors accounted, respectively, for only 13% and 7% of the production rate reported in sugarcane vinasse AD at 55 °C. At 70 °C, the main genera responsible for methane production was Methanothermobacter and the acetoclastic methanogenesis did not occur, resulting in acetic acid build up (15,800 mg L−1). These results brought a new perspective for sugarcane vinasse management, with acetic acid production alternatively to methanization. In this perspective, two-stage process would be composed of acidogenic and acetogenic reactors, and beyond acetate, hydrogen and other soluble compounds could be recovered in a complete biorefinery process. [ABSTRACT FROM AUTHOR]