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This study aimed at investigating the feasibility of using a highly specialized bacterial inoculum harboring lactic acid bacteria (LAB) and lactate-oxidizing, hydrogen-producing bacteria (LO-HPB) to produce either lactate or biohydrogen and butyrate from several agro-industrial resources via dual-phase dark fermentation. The feedstocks were fruit–vegetable waste, cheese whey, coffee wastewater, tequila vinasse, and maize processing wastewater, and were tested in both mono- and co-fermentation. The results obtained indicated that the biocatalyst used was able to perform a dual-phase lactate fermentation, producing high lactate (13.1–36.4 g/L), biohydrogen (0.2–7.5 NL H2/Lfeedstock, equivalent to 0.3–1.7 mol H2/mol hexose), and butyrate (3.3–13.9 g/L) with all the tested feedstocks. A series of self-fermentation tests were also performed with crude cheese whey and fruit–vegetable waste for comparison purposes. Compared to inoculum-aided fermentations, the self-fermentation exhibited a reduced bioconversion efficiency. Short-length 16S rRNA gene sequencing analysis showed that LO-HPB was the dominant microbial group (86.0%) in the biocatalyst, followed by acetic acid bacteria (5.8%) and LAB (5.7%). As expected, the molecular analysis also showed significant differences in the microbial community structure of the biocatalyst and those that evolved from self-fermentation. Besides lactate fermentation and oxidation, the biocatalyst also assisted the bi-phasic lactate fermentation via oxygen consumption, and apparently, via substrate hydrolysis. Overall, this study can lay the foundation for robust inoculum development, which is of special significance in the field of dark fermentation, and proposes an innovative bioprocess for agro-industrial valorization through a trade-off approach, tailoring the metabolic pathway to the target product(s).

Assessment of wastewater effluent quality in terms of physicochemical and microbial parameters is a difficult task; therefore, an online method which combines the variables and represents a final value as the quality index could be used as a useful management tool for decision makers. However, conventional measurement methods often have limitations, such as time-consuming processes and high associated costs, which hinder efficient and practical monitoring. Therefore, this study presents an approach that underscores the importance of using both short- and long-term memory networks (LSTM) to enhance monitoring capabilities within wastewater treatment plants (WWTPs). The use of LSTM networks for soft sensor design is presented as a promising solution for accurate variable estimation to quantify effluent quality using the total chemical oxygen demand (TCOD) quality index. For the realization of this work, we first generated a dataset that describes the behavior of the activated sludge system in discrete time. Then, we developed a deep LSTM network structure as a basis for formulating the LSTM-based soft sensor model. The results demonstrate that this structure produces high-precision predictions for the concentrations of soluble X1 and solid X2 substrates in the wastewater treatment system. After hyperparameter optimization, the predictive capacity of the proposed model is optimized, with average values of performance metrics, mean square error (MSE), coefficient of determination (R2), and mean absolute percentage error (MAPE), of 23.38, 0.97, and 1.31 for X1, and 9.74, 0.93, and 1.89 for X2, respectively. According to the results, the proposed LSTM-based soft sensor can be a valuable tool for determining effluent quality index in wastewater treatment systems.

The high loading of lactic acid bacteria (LAB) present in cheese whey still limits its use as hydrogen feedstock. This study aims to investigate the feasibility of producing hydrogen from acid cheese whey via lactate-driven dark fermentation (LD-DF). Mesophilic batch fermentations were performed with delipidated acid cheese whey at a fixed pH of 5.8 and driven by an acidogenic bacterial culture containing LAB and lactate-oxidizing hydrogen producers (LO-HPB). The results obtained indicated that it is technically feasible to produce hydrogen from undiluted cheese whey through lactate oxidation-mediated fermentation. It was elucidated that the acidogenic fermentation of cheese whey followed a two-step lactate-type fermentation, in which fermentable carbohydrates were first converted into lactate, and then lactate was metabolized into hydrogen with the co-production of butyrate. The hydrogen yield and the maximum volumetric hydrogen production rate achieved were 44.5 ± 2.9 NmL/g-CODfed and 1.9 NL/L-d, respectively. Further microbial community analysis revealed that Lactobacillus, Clostridium, and Klebsiella were the dominant bacterial genera when the hydrogen production rate peaked. It was therefore suggested that the metabolic potential behind the association between LAB and LO-HPB was important in driving the two-step lactate-type fermentation. Overall, the LD-DF can be a strategic hydrogen-producing pathway to be implemented with cheese whey.

The technical feasibility of valorizing tequila vinasse (TV), a wastewater with high pollution potential, through the production of biogenic hydrogen via dark fermentation, has long been proven in diverse lab-scale reactors that were operated either in batch or continuous mode. However, such systems have mainly been tested with diluted streams and nutrient supplementation, hindering the techno-economic attractiveness of the TV-to-hydrogen concept at large scale. In this study, the feasibility of producing hydrogen from high-strength undiluted TV with no added extra nutrients was evaluated under batch mesophilic conditions. Additionally, the use of two different acidogenic inocula obtained either by heat or heat-aeration pretreatment was investigated to get a greater understanding of the effect of inoculum type on the process. The results obtained showed that the TV utilized herein contained macro- and micro-nutrients high enough to support the hydrogenogenic activity of both cultures, entailing average hydrogen yields of 2.4–2.6 NL H2/L vinasse and maximum hydrogen production rates of 1.4–1.9 NL H2/L-d. Interestingly, the consumption of lactate and acetate with the concomitant production of butyrate was observed as the main hydrogen-producing route regardless of the inoculum, pointing out the relevance of the lactate-driven dark fermentative process. Clostridium beijerinckii was ascertained as key bacteria, but only in association with microorganisms belonging to the genera Enterobacter and Klebsiella, as revealed by phylogenetic analyses.

The use of metal nanoparticles (NPs) to enhance hydrogen production in dark fermentation (DF) has become a pioneering field of interest. In particular, iron-based nanoparticles (FeNPs) play a pivotal role in enhancing the activity of metalloenzymes and optimizing feedstock utilization, resulting in improved hydrogen production. This study investigated the effect of FeNPs (magnetite) supplementation at three different concentrations of 50, 100, and 200 ppm in a continuous dark fermenter for the production of hydrogen from rice straw acid hydrolysate. The highest hydrogen production rate of 2.6 ± 0.3 NL H2/L-d was achieved with the addition of 100 ppm of nanoparticles, representing a 53% increase compared to the condition without FeNPs addition. This improvement was driven by a microbial community in which Clostridium was the major dominant genus. In addition, increasing the nanoparticle concentration to 100 ppm resulted in an increase in butyrate concentration to 2.0 ± 0.1 g/L, which is 43% higher than the butyrate concentration without FeNPs. However, when the NP concentration was increased to 200 ppm, the hydrogen production rate decreased to 1.6 ± 0.2 NL H2/L-d. This study can serve as a guideline for future research aimed at evaluating the effects of FeNPs in continuous dark fermentation systems. This work highlights the potential benefits and challenges associated with the use of FeNPs, paving the way for future studies to optimize their application and improve the efficiency of dark fermentation processes.

In recent years, the research community is tremendously investigating unexplored plants and herbals as they represent a potential source of various biomolecules, which not only contribute to nutrition but also to human health. In fact, Muicle (Justicia spicigera) has attracted the attention of scientists thanks to its multiple biological activities associated with the phytochemicals and specific biomolecules present in this plant. In this review, an evidence on current development works assaying the potential biological properties of Muicle is given. Here, we introduce the key biologically active molecules ascribed to such properties, along with the mechanism of action and interaction. Although the utilization of this plant has been majorly focused on traditional medicine, specific applications in terms of production of new feedstocks and nanomaterials, and developments of functional foods and formulations, are also a current direction towards the exploitation of this natural source. Therefore, this review reports the main outcomes of current research towards the utilization of biomolecules and other elements of the plant in new fields of research such as materials chemistry.

The combined effects of three key ozonation process parameters on the integrated ozonation-enzymatic hydrolysis pretreatment of sugarcane bagasse (SCB) were investigated, with emphasis on the relationship between sugar release and ozone consumption. A lab-scale fixed bed reactor was employed for ozonation at varying ozone doses (50, 75 and 100 mg O3/g SCB), particle sizes (420, 710 and 1000 µm) and moisture contents (30, 45 and 60% w/w) in multifactorial experiments, keeping a residence time of 30 min. The ozonated SCB showed a reduction in the content of acid-insoluble lignin from 26.6 down to 19.1% w/w, while those of cellulose and hemicellulose were retained above 45.5 and 13.6% w/w, with recoveries of 100–89.9 and 83.5–72.7%, respectively. Ozone-assisted enzymatic hydrolysis allowed attaining glucose and xylose yields as high as 45.0 and 37.8%, respectively. The sugars released/ozone expended ratio ranged between 2.3 and 5.7 g sugars/g O3, being the higher value achieved with an applied ozone input of 50 mg O3/g SCB and SCB with 420 µm particle size and 60% moisture. Such operating conditions led to efficient ozone utilization (<2% unreacted ozone) with a yield of 0.29 g sugars/g SCB. Overall, the amount of sugars released relative to the ozone consumed was improved, entailing an estimated cost of ozonation of USD 34.7/ton of SCB, which could enhance the profitability of the process.

Temporal delays and spatial randomness between ground-based data and satellite overpass involve important deviations between the empirical model output and real data; these are factors poorly considered in the model calibration. The inorganic matter-generated turbidity in Lake Chapala (Mexico) was taken as a study case to expose the influence of such factors. Ground-based data from this study and historical records were used as references. We take advantage of the at-surface reflectance from Landsat-8, sun-glint corrections, a reduced NIR-band range, and null organic matter incidence in these wavelengths to diminish the physical phenomena-related radiometric artifacts; leaving the spatio-temporal relationships as the principal factor inducing the model uncertainty. Non-linear correlations were assessed to calibrate the best empirical model; none of them presented a strong relationship (<73%), including that based on hourly delays. This last model had the best predictability only for the summer-fall season, explaining 71% of the turbidity variation in 2016, and 59% in 2017, with RMSEs < 24%. The instantaneous turbidity maps depicted the hydrodynamic complexity of the lake, highlighting a strong component of spatial randomness associated with the temporal delays. Reasonably, robust empirical models will be developed if several dates and sampling-sites are synchronized with more satellite overpasses.

The production of Tequila (55% Alc. Vol.) in Mexico for the year 2008 was 227 million liters, and consequently around 2,270 million liters of Tequila vinasses (TVs) were generated, which without proper treatment is equivalent to the pollution produced by 6.2 million people. The lack of both finances and technology availability are reasons for the absence of wastewater treatment plants (WTP) in the Tequila factories, with the exception of some big and medium size factories. There are WTPs based on both biological and physicochemical processes and also combinations of them that have been implemented to treat TVs; however, in most of the cases the implementation has not been effective. The WTPs that utilize a biological anaerobic process seem to be the most suitable for the treatment of TVs; however, there are some technical factors that have to be considered before the implementation of a technological solution for this environmental issue. This mini-review presents the state of the art of wastewater treatments performance in the Tequila industry, discussing the efficacy of the systems together with other technologies that could be considered to fulfill the requirements for the environmental regulation in Mexico.

Endocrine-disrupting chemicals can produce effects on the human health or living beings. Hence, it is of high importance to determine their presence in water. This work presents a reliable method for determining 17β-Estradiol (E 2 ) and 17α-Ethinylestradiol (EE 2 ) in tap and drinking water. The analytic method proposed was optimized by spiking ultrapure water samples with a known amount of steroids in terms of solid phase extraction by varying elution solvent volume and analyte mass in the cartridge, the extract concentration by using either distinct temperatures in rotary evaporator or nitrogen gentle stream, and the solvent effect in chemical derivatization with N , O -bis (trimethylsilyl) trifluoroacetamide:trimethylchlorosilane (1%). The performance of the analytical method was assessed and applied to real samples; the efficiency of extraction and derivatization procedure ranged from 81 to 100% for E 2 (CV 4–19%) and from 82 to 96% for EE 2 (CV 4–18%). Limits of detection (quantification) were 1.0 (3.0) ng/L and 3.0 (10.0) ng/L for E 2 and EE 2 , respectively. Analysis of the drinking water samples yielded concentrations ranging from 3.0 to 11.4 ng/L for E 2 and from 10.0 to 246 ng/L for EE 2 . Analyses of steroids in tap water were found below the limit of detection. Consumption of drinking water in the presence of endocrine-disrupting chemicals could be a risk for the users in the long term and their consumption should be avoided under the principle of prevention.