Anaerobic Fermentation Process Research Articles

WEBINAR SEBAGAI SARANA SOSIALISASI PENGOLAHAN LIMBAH ORGANIK MENJADI EKO-ENZIM

Organic waste resulting from anthropogenic and industrial activities has become a source of pollution that can disrupt the existence of the environment. Various efforts have been made to minimize the presence of these sources of pollution, including processing them into more useful products. Eco-enzymes are a product that can be produced from organic waste which is processed through an anaerobic fermentation process. This online community service activity packaged through a webinar aims to be a means of communication and socialization media to raise public awareness about the urgency of managing organic waste as well and provide new insights in processing organic waste into more useful products in the form of eco-enzymes. The method used was participatory through an online seminar involving 144 participants from various backgrounds of regional, scientific disciplines, professions, and social status. The results of this activity show that there is enthusiasm among the participants in discussions regarding the use and processing of organic waste into eco-enzymes. This webinar is also able to build good communication and interpersonal interaction patterns, discussion and elaboration of material becomes more constructive, and reaches many participants from various regions, scientific disciplines, professions, and social status.

Unraveling the effects and mechanisms of microplastics on anaerobic fermentation: Exploring microbial communities and metabolic pathways

To investigate the effects of microplastics (MPs) on hydrolysis, acidification and microbial characteristics during waste activated sludge (WAS) anaerobic fermentation process, five different kinds of MPs were added into the WAS fermentation system and results indicated that, compared to the control group, the addition of polyvinyl chloride (PVC)-MPs exhibited the least inhibition on volatile fatty acids (VFAs), reducing them by 13.49 %. Conversely, polyethylene (PE)-MPs resulted in the greatest inhibition, with a reduction of 29.57 %. MPs, while accelerated the dissolution of WAS that evidenced by an increase of lactate dehydrogenase (LDH) release, concurrently inhibited the activities of relevant hydrolytic enzymes (α-Glucosidase, protease). For microbial mechanisms, MPs addition affected the proliferation of key microorganisms (norank_f_Bacteroidetes_vadinHA17, Ottowia, and Propioniclava) and reduced the abundance of genes associated with hydrolysis and acidification (pfkb, gpmI, ilvE, and aces). Additionally, MPs decreased the levels of key hydrolytic and acidogenic enzymes to inhibit hydrolysis and acidification processes. This research provides a basis for understanding and unveils impact mechanisms of the impact of MPs on sludge anaerobic fermentation.

Resident gut microbiota community determines the efficacy of soluble fiber in reducing adiposity.

Consumption of dietary fiber has been linked to several health benefits. Among these, dietary fiber breakdown through the process of anaerobic fermentation by the colonic microbiota leads to the production of beneficial metabolites, mainly short-chain fatty acids (acetate, propionate, and butyrate), which have been implicated in reduced calorie intake. Nevertheless, the link between gut microbiota and obesity remains unclear. We investigated the effects of dietary fibers on food intake and body weight gain in two independent but similarly designed studies in rats. In the first study, the inclusion of 10% w/w pectin, fructooligosaccharides or beta-glucan (n = 10/group) in the diets each significantly reduced body weight gain ('responders') compared to the cellulose control whereas, in a closely matched, but not fully identical study (n = 8/group), no effect of dietary fiber on body weight ('non-responders') was observed. The aim of this work was to explore the basis of this differential response between the two similarly designed and comparable studies, with a focus on the potential role of the gut microbiota in the control of food intake and body weight.

Study on the removal of high nitrate-nitrogen concentration from pig farm wastewater by heterotrophic and sulphur autotrophic synergistic denitrification filter process

Following the anaerobic fermentation process in a lagoon, the effluent from pig wastewater exhibited elevated levels of total nitrogen and nitrate nitrogen. The utilization of simple sulphur-limestone autotrophic denitrification resulted in a sluggish reaction rate and relatively moderate removal load. To enhance the efficacy of the sulphur autotrophic denitrification process, a strategy was implemented involving the introduction of a limited quantity of corncobs as a slow-release carbon source. This addition was made to a sulphur-limestone autotrophic denitrification reactor that was being operated continuously and stably. Furthermore, the volume ratio of the corncobs added was progressively increased. This study examines the alterations in nitrate nitrogen, chemical oxygen demand (COD), sulphate, and alkali consumption within the sulphur-limestone autotrophic denitrification reactor, both prior to and after the introduction of corncobs. This study examines the operational efficiency and reaction mechanism of a sulfur-limestone autotrophic denitrification reactor that is enhanced by the utilization of corncobs as a slow-release carbon source. The findings of the study indicate that the inclusion of maize cob carbon source in the sulphur limestone autotrophic denitrification process resulted in improved effectiveness in removing nitrate and nitrogen. Additionally, when considering the three different ratios of corncob carbon source, the process exhibited a chemical oxygen demand (COD) removal rate exceeding 42%. The observed trend in the consumption of alkalinity in both the pure sulphur limestone autotrophic denitrification process and the sulphur limestone autotrophic denitrification process augmented by the three types of corncob slow-release carbon sources indicated an increase with time. The concentration of nitrate-nitrogen in the influent water exhibited a negative correlation with the length of the reactor flow-through. The addition of a slow-release carbon source derived from corncob greatly enhanced the autotrophic denitrification and denitrification impact in the three reactors. Moreover, there was an observed increase in the trend of heterotrophic denitrification as the amount of carbon source added increased. The efficacy of the mixotrophic denitrification process surpassed that of the sulphur-limestone autotrophic denitrification method in the treatment of nitrate-nitrogen wastewater characterized by a high concentration of nitrate-nitrogen. The former exhibited a higher denitrification rate and resulted in lower levels of sulphate ions and alkalinity production.

Research on the Resource Recovery of Medium-Chain Fatty Acids from Municipal Sludge: Current State and Future Prospects.

The production of municipal sludge is steadily increasing in line with the production of sewage. A wealth of organic contaminants, including nutrients and energy, are present in municipal sludge. Anaerobic fermentation can be used to extract useful resources from sludge, producing hydrogen, methane, short-chain fatty acids, and, via further chain elongation, medium-chain fatty acids. By comparing the economic and use values of these retrieved resources, it is concluded that a high-value resource transformation of municipal sludge can be achieved via the production of medium-chain fatty acids using anaerobic fermentation, which is a hotspot for future research. In this study, the selection of the pretreatment method, the method of producing medium-chain fatty acids, the influence of the electron donor, and the technique used to enhance product synthesis in the anaerobic fermentation process are introduced in detail. The study outlines potential future research directions for medium-chain fatty acid production using municipal sludge. These acids could serve as a starting point for investigating other uses for municipal sludge.

Salt and heat stress enhances hydrogen production in cyanobacteria.

Cyanobacteria are among the most suitable organisms for the capture of excessive amounts of CO2 and can be grown in extreme environments. In our research we use the single-celled freshwater cyanobacteria Synechococcus elongatus PCC7942 PAMCOD strain and Synechocystis sp. PCC6714 for the production of carbohydrates and hydrogen. PAMCOD strain and Synechocystis sp. PCC6714 synthesize sucrose when exposed to salinity stress, as their main compatible osmolyte. We examined the cell proliferation rate and the sucrose accumulation in those two different strains of cyanobacteria under salt (0.4M NaCl) and heat stress (35 0C) conditions. The intracellular sucrose (mol sucrose content per Chl a) was found to increase by 50% and 108% in PAMCOD strain and Synechocystis sp. PCC6714 cells, respectively. As previously reported, PAMCOD strain has the ability to produce hydrogen through the process of dark anaerobic fermentation (Vayenos D, Romanos GE, Papageorgiou GC, Stamatakis K (2020) Photosynth Res 146, 235-245). In the present study, we demonstrate that Synechocystis sp. PCC6714 has also this ability. We further examined the optimal conditions during the dark fermentation of PAMCOD and Synechocystis sp. PCC6714 regarding H2 formation, increasing the PAMCOD H2 productivity from 2 nmol H2 h- 1 mol Chl a- 1 to 23 nmol H2 h- 1 mol Chl a- 1. Moreover, after the dark fermentation, the cells demonstrated proliferation in both double BG-11 and BG-11 medium enriched in NaNO3, thus showing the sustainability of the procedure.

Performance evaluation of Anaerobic-Aerobic Hybrid Baffled Reactor Coupled with an Anaerobic Filter treating Landfill Leachate.

The Anaerobic Baffled Reactor (ABR) is an effective solution for landfill leachate treatment using an anaerobic fermentation process, which helps to reduce operating costs and sludge volume. To better understand the biological, chemical, and physical processes involved, especially when combining the ABR with an aerobic component, the study aimed to investigate the performance of an Anaerobic-Aerobic Hybrid Baffled Reactor (AABR) that includes an Anaerobic Filter (AF) for treating landfill leachate. This research utilized two glass reactors. The first reactor, designated as AABR-AF, consisted of six independent rectangular glass chambers arranged side by side. The third and sixth chamber designed for aerobic treatment and AF, respectively. The second reactor was used as a control reactor and did not include any aerobic chamber. The highest Removal Efficiencies (REs) for turbidity, COD, BOD, TP, TKN, nitrate, TOC, and TSS in the AABR-AF and ABR-AF were found to be (65.4% and 56.3%), (98.3% and 94.1%), (98.1% and 93.2%), (86.4% and 65%), (89.2% and 76.7%), (81.2% and 64.4%), (88.2% and 79.4%), and (72.4% and 68.5%), respectively. These optimal REs were achieved at an HRT of 48 h and an OLR of 10 kg/m3.d. Also, the highest and the lowest REs in Heavy Metals (HMs) were 89.57% for manganese in AABR-AF and 6.59% for nickel in ABR-AF, in an OLR of 10 kg/m3.d, respectively. The effective removal of Organic Matters (OMs) from landfill leachate using the AABR-AF and ABR-AF was found to be strongly influenced by HRT and OLR. The AABR-AF configuration, featuring a single aerobic chamber in the reactor, exhibited a higher efficiency in removing OMs compared to the ABR-AF configuration.

Mechanism and Effect of Amino Acids on Lactic Acid Production in Acidic Fermentation of Food Waste

Amino acids, particularly the ones that cannot be synthesised during fermentation, are reportedly to be key nutrients for anaerobic fermentation processes, and some of the acids are also intermediate products of anaerobic fermentation of protein-rich waste. To date, particularly, there is a lack of research on the effects of some amino acids, such as cysteine, glycine, aspartic acid, and valine, on lactic production from the fermentation of food waste and also the mechanisms involved in the process. Thus, this study investigated the effects of the four different amino acids on lactic acid production during the acidic anaerobic fermentation of food waste. Firstly, batch experiments on synthetic food waste at different pHs (4.0, 5.0, and 6.0) were executed. The results harvested in this study showed that higher LA concentrations and yields could be obtained at pH 5.0 and pH 6.0, compared with those at pH 4.0. The yield of lactic acid was slightly lower at pH 5.0 than at pH 6.0. Furthermore, caustic consumption at pH 5.0 was much lower. Therefore, we conducted batch experiments with additions of different amino acids (cysteine, glycine, aspartic acid, and valine) under pH 5.0. The additions of the four different amino acids showed different or even opposite influences on LA production. Glycine and aspartic acids presented no noticeable effects on lactic acid production, but cysteine evidently enhanced the lactic acid yield of food waste by 13%. Cysteine addition increased α-glucosidase activity and hydrolysis rate and simultaneously enhanced the abundance of Lactobacillus at the acidification stage as well as lactate dehydrogenase, which also all favoured lactic acid production. However, the addition of valine evidently reduced lactic acid yield by 18%, and the results implied that valine seemingly inhibited the conversion of carbohydrate. In addition, the low abundance of Lactobacillus was observed in the tests with valine, which appeared to be detrimental to lactic acid production. Overall, this study provides a novel insight into the regulation of lactic acid production from anaerobic fermentation of food waste by adding amino acids under acidic fermentation conditions.

Study on the mechanism of action of methane production by co-fermentation of sludge and lignite.

To improve the methanogenic efficiency of lignite anaerobic fermentation and explore innovative approaches to sludge utilization, a co-fermentation technique involving lignite and sludge was employed for converting biomass into biomethane. Volatile suspended solids were introduced as a native enrichment of the sludge and mixed with lignite for fermentation. The synergistic fermentation mechanism between sludge and lignite for biomethane production was analyzed through biochemical methane potential experiments, measurement of various parameters pre- and post-fermentation, observation of bacterial population changes during the peak of reaction, carbon migration assessment, and evaluation of rheological characteristics. The results showed that the addition of sludge in the anaerobic fermentation process improved the microorganisms' ability to degrade lignite and bolstered biomethane production. Notably, the maximum methane production recorded was 215.52mL/g-volatile suspended solids, achieved at a sludge to coal ratio of 3:1, with a synergistic growth rate of 25.37%. Furthermore, the removal rates of total suspended solids, and total chemical oxygen demand exhibited an upward trend with an increasing percentage of sludge in the mixture. The relative abundance and activity of the methanogens population were found to increase with an appropriate ratio of sludge to lignite. This observation confirmed the migration of carbon between the solid-liquid-gas phases, promoting enhanced system affinity. Additionally, the changes in solid-liquid phase parameters before and after the reaction indicated that the addition of sludge improved the system's degradation capacity. The results of the study hold significant implications in realizing the resource utilization of sludge and lignite while contributing to environmental protection endeavors.

Mechanism of improving anaerobic fermentation performance of kitchen waste pretreated by ionizing irradiation-part 1: rice.

Ionizing irradiation, as a new pretreatment method for the anaerobic fermentation of organic pollutants, is featured with fast reaction speed, good treatment effect, no need to add any chemical reagents, and no secondary pollution. This study explores the mechanism of improving anaerobic fermentation performance of rice samples pretreated by cobalt-60 gamma irradiation through the influence on fermentation substrate, acidogenic phase and methanogenic phase. The results reveal that the soluble chemical oxygen demand of the irradiated rice sample at an absorbed dose of 9.6 kGy increases by 12.4 times due to the dissolution of small molecules of fat-soluble organic matter. The yield of biogas in the acidogenic phase increases by 22.2% with a slight increase in hydrogen gas content. The yield of biogas and methane gas content in the methanogenic phase increases by 27.3% and 15%, respectively. Microbial genome analysis, performed with MiSeq high-throughput sequencing and metagenomic methods, suggests the microbial abundance and metabolic functions in the anaerobic fermentation process change significantly as a result of the pretreatment by gamma irradiation.

The Difference in the Source of Bee Bread (Citrus, Anise) in Its Chemical Composition

Beebread is a hive product derived from the collection of pollen by bees. To produce beebread, bees enrich the gathered pollen with honey and digestive enzymes, storing the mixture within the combs. The transformation of bee pollen into beebread occurs through an anaerobic fermentation process facilitated by the bees.
 Effective beehive management is crucial to encourage the accumulation of beebread, with the intention of marketing it for human consumption. This is due to its recognition as a valuable nutritional supplement, attributed to its rich array of nutrients. The nutritional value of beebread, including protein, amino acids, fatty acids, carbohydrates, and polyphenols, is contingent upon the plant source of the bee pollen, emphasizing the significance of proper hive management for optimizing its quality.
 The nutritional and functional composition of beebread lead this research, work was done to collect bee bread from two different geographical regions, namely the coastal region (Lattakia), which was the predominant citrus at the time of collection and the interior region (the countryside of Hama), which was aniseed prevalent at the time of collection.
 The results of the research showed the difference in the chemical composition of bee bread collected from the two mentioned areas.
 The protein content of bee bread samples from the interior region increased, which amounted to 20%, with a very high significance compared to bee bread from the coastal region, which amounted to 15.6%.
 The content of sinters also increased with a very high significance, which amounted to 7.92% and 2.02% in the interior and coastal regions, respectively.
 As for the ash, it was 2% and 1.3% in the interior and coastal regions, respectively.
 As for the humidity of the samples of the interior region, it was lower than that of the coastal region, which amounted to 8.68%, while 13.5% in the coastal region.
 The results also showed the difference in the content of the studied bee bread samples in fructose, where the content of the samples of the interior region amounted to 23.07%, while the content of the samples of the coastal region amounted to 18.10%, while the content of glucose sugar reached 15.74% and 14.82% in both the interior and coastal regions, respectively.
 This confirms the difference in the chemical composition of bee bread according to the plant type from which bee pollen was collected.

Carbon source fate in lysozyme-assistant anaerobic fermentation process of excess sludge: interphase carbon migration, recovery and extraction

Lysozyme has been regarded as promising approach to enhance anaerobic fermentation of excess sludge. However, little investigation has revealed the specific patterns of interphase carbon source migration and recovery. This study demonstrated that the rising lysozyme dosages greatly improved the kinetics and performances of endogenous carbon source release and biotransformation, which mainly occurred within 48-h treatment. Considerable 146.66 mg C/g VSS particulate carbon sources were solubilized from sludge solid, composing of proteins, humic acids and metabolic intermediates. Meanwhile, almost 57.48 % of the originally released carbon sources were bio-transformed into short-chain fatty acids with accelerated sludge acidification, which were regarded as the recoverable carbon source. Correspondingly, considerable carbon recovery of 103.18 mg C/g VSS was achievable by lysozyme assistance in 96-h anaerobic fermentation. Such lysozyme catalysis strategy improved carbon migration and recovery by 5.38 and 6.21 times, respectively. The fermented sludge was easily dewatered after chemical conditioning, thereby the effective carbon source extraction was implemented by solid-liquid separation. Approximately 65.99–87.02 % of the recoverable carbon sources were remained in fermentative liquid. The high ratios of carbon sources to nutrients (nitrogen and phosphorus) suggested favorable bio-availability and utilizability of the recoverable carbon sources. The overall carbon flow and migration pathways in lysozyme-driven patterns were illustrated to directly clarify the carbon source fate in anaerobic fermentation process and carbon recovery benefits from excess sludge.

Dynamic microbiome disassembly and evolution induced by antimicrobial methylisothiazolinone in sludge anaerobic fermentation for volatile fatty acids generation

In the post-COVID-19 pandemic era, various antimicrobials have emerged and concentrated in waste-activated sludge (WAS), affecting the biological treatment of WAS. However, there is still a knowledge gap in the dynamic response and adaptive mechanism of anaerobic microbiome under exogenous antimicrobial stress. This study found that methylisothiazolinone (MIT, as a typic antimicrobial) caused an interesting lag effect on the volatile fatty acids (VFAs) promotion in the WAS anaerobic fermentation process. MIT was effective to disintegrate the extracellular polymeric substances (EPS), and those functional anaerobic microorganisms were easily exposed and negatively impacted by the MIT interference after the loss of protective barriers. Correspondingly, the ecological interactions and microbial metabolic functions related to VFA biosynthesis (e.g., pyruvate metabolism) were downregulated at the initial stage. The syntrophic consortia gradually adapted to the interference and attenuated the MIT stress by activating chemotaxis and resistance genes (e.g., excreting, binding, and inactivating). Due to the increased bioavailable substrates in the fermentation systems, the dominant microorganisms (i.e., Clostridium and Caloramator) with both VFAs production and MIT-tolerance functions have been domesticated. Moreover, MIT disrupted the syntrophic interaction between acetogens and methanogens and totally suppressed methanogens' metabolic activities. The VFA production derived from WAS anaerobic fermentation was therefore enhanced due to the interference of antimicrobial MIT stress. This work deciphered dynamic changes and adaptive evolution of anaerobic syntrophic consortia in response to antimicrobial stress and provided guidance on the evaluation and control of the ecological risks of exogenous pollutants in WAS treatment.

Simple Methods for Observing and Utilizing Biogas as a Renewable Energy Source

One combustible and burnable gas that can be created through an anaerobic fermentation process is biogas. An anaerobic process occurs when organic material, like animal dung, is processed in a digester (reactor) without the presence of oxygen. This observation's objectives are to (i) disseminate knowledge about the biogas production process and (ii) acquire a generation system for producing biogas. The observation methods are based on the use of an observation algorithm in the form of a flow chart, and it includes (a) observations related to various stages of choosing the type of installation, the requirements and processes for the formation of biogas observed and utilized from readily available organic materials, and influencing factors; and (b) observations related to the generation system for the production of biogas observed and utilized, including the physical reservoir, the amount of biogas produced, and the biogas utilized for supply to the electricity generator. The results of the observations related to the generation system, including the physical reservoir, the amount of biogas produced, and the biogas used for supplying the electricity generator, while the results of the observations related to the biogas production process, including the availability of installations, requirements and processes for biogas production, and influencing factors for the formation of biogas. Based on these findings, it can be said that the best period of time for biogas production is between 14 and 16 days, with a production volume of 6.0 m3 /day. While 0.64 m3 of biogas is needed for electric lighting, 0.30 m3 /hour of biogas at a pressure of 75 mm H2O is needed for cooking activities. While pure methane gas has an energy content of 8,900 kcal/m3 , the resulting calorific value is relatively high, ranging from 4,800 to 6,700 kcal/m3.

Biotechnological Valorization of Waste Glycerol into Gaseous Biofuels—A Review

The supply of waste glycerol is rising steadily, partially due to the increased global production of biodiesel. Global biodiesel production totals about 47.1 billion liters and is a process that involves the co-production of waste glycerol, which accounts for over 12% of total esters produced. Waste glycerol is also generated during bioethanol production and is estimated to account for 10% of the total sugar consumed on average. Therefore, there is a real need to seek new technologies for reusing and neutralizing glycerol waste, as well as refining the existing ones. Biotechnological means of valorizing waste glycerol include converting it into gas biofuels via anaerobic fermentation processes. Glycerol-to-bioenergy conversion can be improved through the implementation of new technologies, the use of carefully selected or genetically modified microbial strains, the improvement of their metabolic efficiency, and the synthesis of new enzymes. The present study aimed to describe the mechanisms of microbial and anaerobic glycerol-to-biogas valorization processes (including methane, hydrogen, and biohythane) and assess their efficiency, as well as examine the progress of research and implementation work on the subject and present future avenues of research.

Safety assessment of a proprietary fermented soybean solution, Symbiota®, as an ingredient for use in foods and dietary supplements: Non-clinical studies and a randomized trial.

A safety evaluation was performed of Symbiota®, which is made by a proprietary anaerobic fermentation process of soybean with multistrains of probiotics and a yeast. The battery of genotoxicity studies showed that Symbiota® has no genotoxic effects. Safety and tolerability were further assessed by acute or repeated dose 28- and 90-day rodent studies, and no alterations in clinical observations, ophthalmological examination, blood chemistry, urinalysis, or hematology were observed between the control group and the different dosing groups (1.5, 5, and 15 mL/kg/day). There were no adverse effects on specific tissues or organs in terms of weight and histopathology. Importantly, the Symbiota® treatment did not perturb hormones and other endocrine-related endpoints. Of note, the No-Observed-Adverse-Effect-Level was determined to be 15 mL/kg/day in rats. Moreover, a randomized, double-blind, placebo-controlled clinical trial was recently conducted with healthy volunteers who consumed 8 mL/day of placebo or Symbiota® for 8 weeks. Only mild adverse events were reported in both groups, and the blood chemistry and blood cell profiles were also similar between the two groups. In summary, this study concluded that the oral consumption of Symbiota® at 8 mL/day by the general population does not pose any human health concerns.

Algorithms for Optimizing Energy Consumption for Fermentation Processes in Biogas Production

Problems related to reducing energy consumption constitute an important basis for scientific research worldwide. A proposal to use various renewable energy sources, including creating a biogas plant, is emphasized in the introduction of this article. However, the indicated solutions require continuous monitoring and control to maximise the installations’ effectiveness. The authors took up the challenge of developing a computer solution to reduce the costs of maintaining technological process monitoring systems. Concept diagrams of a metrological system using multi-sensor techniques containing humidity, temperature and pressure sensors coupled with Electrical Impedance Tomography (EIT) sensors were presented. This approach allows for effective monitoring of the anaerobic fermentation process. The possibility of reducing the energy consumed during installation operation was proposed, which resulted in the development of algorithms for determining alarm states, which are the basis for controlling the frequency of technological process measurements. Implementing the idea required the preparation of measurement infrastructure and an analytical engine based on AI techniques, including an expert system and developed algorithms. Numerous time-consuming studies and experiments have confirmed reduced energy consumption, which can be successfully used in biogas production.

Transcriptomic and metabolomic approaches elucidate the systemic response of wheat plants under waterlogging.

Extreme weather conditions lead to significant imbalances in crop productivity, which in turn affect food security. Flooding events cause serious problems for many crop species such as wheat. Although metabolic readjustments under flooding are important for plant regeneration, underlying processes remain poorly understood. Here, we investigated the systemic response of wheat to waterlogging using metabolomics and transcriptomics. A 12 d exposure to excess water triggered nutritional imbalances and disruption of metabolite synthesis and translocation, reflected by reductions in plant biomass and growth performance. Metabolic and transcriptomic profiling in roots, xylem sap, and leaves indicated anaerobic fermentation processes as a local response in roots. Differentially expressed genes and ontological categories revealed that carbohydrate metabolism plays an important role in the systemic response. Analysis of the composition of xylem exudates revealed decreased root-to-shoot translocation of nutrients, hormones, and amino acids. Interestingly, among all metabolites measured in xylem exudates, alanine was the most abundant. Immersion of excised leaves derived from waterlogged plants in alanine solution led to increased leaf glucose concentration. Our results suggest an important role of alanine not only as an amino-nitrogen donor but also as a vehicle for carbon skeletons to produce glucose de novo and meet the energy demand during waterlogging.

Enhancing the volatile fatty acids production from food waste as well as polylactate plastic degradation by coupled with hydrothermal pretreatment

Aspolylactate plastic (PLA)degradationis unsatisfactory in the mesophilic anaerobic fermentation process,this work aimed to unveil the influence of PLA on the characteristics of food waste acidogenic fermentation and enhance the volatile fatty acids (VFAs) production as well as PLA degradation by hydrothermal treatment. The addition of PLA slightly increased the VFAs yield by 6.05 %, while its mass loss rate was only 1.09 % after 12 d fermentation. Hydrothermal treatment could effectively promote the PLA degradation and the dissolution of organic matter in PLA-containing food waste, and 160 °C as well as 40 and 60 min were the ideal hydrothermal conditions with high PLA degradation rate (more than 86 %) and soluble organic materials. In addition, VFAs production from PLA-containing food waste was significantly enhanced by hydrothermal treatment. The maximum yield was obtained under the condition of 160 °C and 60 min, which was 110.06 % higher than the blank group. Moreover, the fermentation time was shortened from 10 d to 4 d.

Revealing the Adverse Impact of Additive Carbon Material on Microorganisms and Its Implications for Biogas Yields: A Critical Review

Biochar could be a brilliant additive supporting the anaerobic fermentation process. However, it should be taken into account that in some cases it could also be harmful to microorganisms responsible for biogas production. The negative impact of carbon materials could be a result of an overdose of biochar, high biochar pH, increased arsenic mobility in the methane fermentation solution caused by the carbon material, and low porosity of some carbon materials for microorganisms. Moreover, when biochar is affected by an anaerobic digest solution, it could reduce the biodiversity of microorganisms. The purpose of the article is not to reject the idea of biochar additives to increase the efficiency of biogas production, but to draw attention to the properties and ways of adding these materials that could reduce biogas production. These findings have practical relevance for organizations seeking to implement such systems in industrial or local-scale biogas plants and provide valuable insights for future research. Needless to say, this study will also support the implementation of biogas technologies and waste management in implementing the idea of a circular economy, further emphasizing the significance of the research.