Bioaugmentation Process Research Articles

Bioaugmentation of microalgae fermentation with yeast for enhancing microbial chain elongation: In-situ ethanol production and metabolic potential

Anaerobic microalgae fermentation, leveraging its cost-effectiveness and the adaptability of mixed cultures, holds promise for carboxylate biosynthesis. Microalgae, with their abundant carbohydrates and proteins, stand out as an optimal substrate for this process among various options. Furthermore, microalgae fermentation not only shows the potential to mitigate risks associated with algae blooms but also aligns with the need for sustainable practices. However, the limited utilization rate of microalgae in anaerobic fermentation poses challenges to achieving high production rates of desired products. In this study, we implemented a bioaugmentation process with yeast to enhance carboxylate production performance of microalgae fermentation. The results demonstrated a fourfold increase in carboxylate yield with the addition of yeast. In-situ ethanol production facilitated the conversion of short-chain carboxylic acids into medium-chain carboxylates, achieving a yield of 46.3 mM-C/g VS. The presence of yeast significantly enhanced substrate utilization from 20 % to 80 %, steering the metabolic pathway towards chain elongation. Metagenomic analysis further revealed metabolic shifts following yeast addition, particularly an increased abundance of genes involved in acetyl-CoA production. Notably, the aldehyde:ferredoxin oxidoreductase (AOR) pathway emerged as a key driver in butanol production. These findings highlight the improved performance of anaerobic microalgae fermentation with yeast, enabling efficient production of higher value bioproducts while eliminating the need for external electron donors.

Valorization of the Caragana waste via two-stage bioaugmentation: Optimizing nutrition composition, palatability, and microbial contaminant control

Caragana korshinskii kom. (CKK) waste, a common forestry byproduct in northwest of China, presents challenges in its transformation into alternative ruminant feed due to its initial nutritional limitations and unappealing palatability. Conventional strategies, such as ensiling and fungal-based solid-state fermentation (SSF) cannot effectively address this issue in practice. Herein, a two-stage bioaugmentation (TBA) process was devised, leveraging the benefits of ensiling and SSF. During the anaerobic ensiling phase, CKK waste was inoculated with Lactiplantibacillus plantarum LP1, effectively suppressing potential animal pathogens such as Aspergillus and Nocardiopsis while enriching the material with potential probiotics like Pediococcus and Lactiplantibacillus, reaching an abundance of 95.7%. In the subsequent aerobic SSF stage, the ensiled CKK underwent inoculation with the white-rot fungus Irpex lacteus F17, which became enriched to 87.9%. Comprehensive multi-omics analysis identified Irpex as the key taxon, possessing an extensive redox enzyme system that led to the improvement in nutrient composition, reduction of astringent phenolic substances, and mitigation of mycotoxins. As a result, the crude protein content of the CKK increased by 39.2%, while lignin, total phenolic substances, and tannic acid content decreased by 24.4%, 52.2%, and 51.4%, respectively. The mycotoxin levels, including aflatoxin B1, zearalenone, and vomitoxin, were rendered negligible, confirming the safety. Overall, this study demonstrates the TBA strategy can successfully transform challenging and unpalatable CKK waste into a nutrient-enriched and safe mycelium-based bioproduct, thereby enabling the valorization of a previously underutilized forestry resource as a promising alternative feed.

Treatment of Diesel-Contaminated Soil by Bioaugmented Composting with Bacteria from the Larva Tenebrio Molitor

In this study, soil composting and bioaugmentation processes were combined to remediate diesel-contaminated soil. Deciduous corn flour, wheat bran, and sawdust were used as co-substrates for soil composting. In addition, consortia of bacteria from the inner tract of the Tenebrio molitor larva were isolated and selected for the bioaugmentation of the composting reactors. It was observed that the isolated inoculum enhanced the treatment and combined with deciduous corn flour, a higher efficiency (87%) and a better removal rate (9.10% diesel removed/week) were registered. In soils with a concentration of 11,796 mg diesel/kg, this combined treatment reduced, in 10 weeks, the pollutant to values below the maximum permissible limits in soils stated by Mexican regulations.

Removal of residual organic pollutants from pulp paper industry wastewater using bacterial strains Acinetobacter baumannii (OK582199) PC4 and Bacillus cereus (OK582201) PC10 via biostimulation and bioaugmentation process

This study examines how native bacteria, combined with two specific aerobic strains (Acinetobacter baumannii PC4 and Bacillus cereus PC10), contribute to the detoxification of pulp and paper industrial wastewater (PPIW) through biostimulation and bioaugmentation processes. The growth of two native bacteria were stimulated in pulp paper industry wastewater by the addition of carbon (1% glucose) and nitrogen (0.5% peptone w/v). After the growth of these native bacteria in biostimulation process showed significant reduction in various physico-chemical parameters i.e. lignin (53%), color (46%), COD (76%), and BOD (86%). Similarly, reductions in various heavy metals were also observed, such as Fe (73%), Zn (36%), Cr (41%), Cu (22%), and Ni (65%). The growing native bacterial co-culture were identified as Enterobacter cloacae strain PC7 (OQ672613) and Bacillus sp. strain PCB (OK614116). However, the addition of Acinetobacter baumannii (OK582199) PC4 and Bacillus cereus (OK582201) PC10 enhanced the reduction of various physico-chemical parameters in range of 10–––28%. Consequently, the UV–Vis absorption peak showed reduction due to the decolorization of wastewater and degradation of various pollutants. Moreover, GC–MS analysis indicated that most of the compounds detected in the control were diminished after bacterial treatment. However, compounds such as Pentadecane, 2-Methyl, Silane (dodecylosy) trimethyl, Octadecanoic acid, trimethylsilyl ester, and Docasane were noted as recalcitrant. Additionally, new metabolic products such as 1-ethyl-5,6-dimethoxy-2,3-dihydroindole, Trimethylsily ether of glycerol, and 1-(Trimethylsilylmethyl1) dimethylsilyloxy tetradecane were detected. Due to degradation of various pollutants toxicity reductions were found up to 76% during a comparative evaluation between control and bacterial treated wastewater using the Phaseolus mungo L. seed germination test. Hence, it was concluded that the biostimulation and bioaugmentation process would be an effective technique for degrading residual organic pollutants from pulp and paper industrial wastewater (PPIW) for safe disposal.

Enhanced phenanthrene biodegradation in river sediments by harnessing calcium peroxide nanoparticles and minerals in Sphingomonas sp. DSM 7526 cultivation

ABSTRACT Coupling chemical oxidation and biodegradation to remediate polycyclic aromatic hydrocarbon (PAH)-contaminated sediment has recently gained significant attention. In this study, calcium peroxide nanoparticles (nCaO2) were utilized as an innovative oxygen-releasing compound for in-situ chemical oxidation. The study investigates the bioremediation of phenanthrene (PHE)-contaminated sediment inoculated with Sphingomonas sp. DSM 7526 bacteria and treated with either aeration or nCaO2. Using three different culture media, the biodegradation efficiencies of PHE-contaminated anoxic sediment, aerobic sediment, and sediment treated with 0.2% w/w nCaO2 ranged from 57.45% to 63.52%, 69.87% to 71.00%, and 92.80% to 94.67%, respectively. These values were significantly higher compared to those observed in non-inoculated sediments. Additionally, the type of culture medium had a prominent effect on the amount of PHE removal. The presence of minerals in the culture medium increased the percentage of PHE removal compared to distilled water by about 2–10%. On the other hand, although the application of CaO2 nanoparticles negatively impacted the abundance of sediment bacteria, resulting in a 30–42% decrease in colony-forming units after 30 days of treatment, the highest PHE removal was obtained when coupling biodegradation and chemical oxidation. These findings demonstrate the successful application of bioaugmentation and chemical oxidation processes for treating PAH-contaminated sediment.

Bioaugmentation treatment of coal chemical reverse osmosis concentrate in biological contact oxidation system coupled with ozone pretreatment

With the zero discharge requirements of coal chemical industry in China, reverse osmosis technology and fractional crystallization technology have been applied to recover water and valuable salts. Organic matter significantly inhibits salt crystallization, therefore it is urgent to remove organic matter from coal chemical reverse osmosis concentrate (CCROC) efficiently and economically. Common biological systems have the bottlenecks of long start-up period and poor pollutants removal efficiency due to the inhibition of toxic compounds and high salinity to the microorganisms. In this work, a self-prepared halotolerant bacteria preparation (HBP, mixture of screened Bacillus, Pseudomonas, and Halomonas with strong degrading capacity of CCROC) was inoculated into different biochemical systems (activated sludge and biological contact oxidation in sequencing batch reactor) to try to enhance the pollutants removal of extremely refractory CCROC (BOD5/COD of 0.05). The results showed that HBP increased the total organic carbon (TOC) removal efficiency from 8% to 15% in activated sludge system. In addition, biological contact oxidation reactor (BCOR) could better retain the HBP, leading to a higher TOC removal efficiency (20%). Typically, the inoculation of HBP without activated sludge in BCOR contributed to the highest TOC removal (28%). The class Bacilli (genus Bacillus) was dominant during the start-up and stable period of this bioaugmented treatment process. To further increase the pollutants removal, ozone oxidation pretreatment was conducted prior to biological treatment to break the ring structures. The total TOC removal increased to 42% under the combined treatment, while the dominant classes in biofilms shifted to Actinobacteria, Gammaproteobacteria, Alphaproteobacteria, and Bacteroidia. This study provided an effective approach for CCROC treatment with industrial application potentials.

Enhanced biodegradation kinetics in the copper-polluted sediment through bioaugmentation with water spinach and peanut husk-derived biochar

Stenotrophomonas maltophilia is a copper-tolerant bacterium that is used for improving the resilience and efficacy of microorganisms engaged in degrading substrate under high copper contamination. Examination of reaction kinetics indicates that the original consortia, Stenotrophomonas maltophilia and the mixed culture, follow a first-order reaction. The Michaelis-Menten model suggests that elevated copper concentrations exert stress on the original bacterial population and Stenotrophomonas maltophilia. However, when a mixed culture is employed during the bioaugmentation process, it brings about an enhancement in microbial resistance and performance. This study demonstrates that the poor performance of indigenous bacteria in media that are highly contaminated with copper can be improved by adding exogenous copper-tolerant bacteria. Furthermore, poor mass transfer in sediments can be improved by adding plants and biochar. This strategic addition serves a dual purpose: it increases the affinity of the substrate for sediments characterized by poor mass transfer and alleviates the inhibitory effects induced by copper. In addition, high percentages of Firmicutes, Bacteroidetes, and Euryarchaeota within the biochar matrix were verified to expedite the substrate biodegradation process even at high copper concentrations. The findings in this work provide an important basis for the future design of in situ bioremediation systems for heavy metal-contaminated sites.

Bioremediation of an industrial soil contaminated by hydrocarbons in microcosm system, involving bioprocesses utilizing co-products and agro-industrial wastes.

The present study describes practical implication of bioaugmentation and biostimulation processes for bioremediation of an industrial soil chronically contaminated by hydrocarbons. For this purpose, biomass production of six autochthonous hydrocarbon-degrading bacteria were evaluated as inoculum of bioaugmentation strategy, by testing carbon and nitrogen sources included co-products and agro-industrial waste as sustainable and low-cost components of the growth medium. Otherwise, biostimulation was approached by the addition of optimized concentration of nitrogen and phosphorus. Microcosm assays showed that total hydrocarbons (TH) were significantly removed from chronically contaminated soil undergoing bioremediation treatment. Systems Mix (bioaugmentation); N,P (biostimulation) and Mix + N,P (bioaugmentation and biostimulation) reached higher TH removal, being 89.85%, 91.00%, 93.04%, respectively, comparing to 77.83% of system C (natural attenuation) at 90days. The increased heterotrophic aerobic bacteria and hydrocarbon degrading bacteria counts were according to TH biodegrading process during the experiments. Our results showed that biostimulation with nutrients represent a valuable alternative tool to treat a chronically hydrocarbon-contaminated industrial soil, while bioaugmentation with a consortium of hydrocarbon degrading bacteria would be justified when the soil has a low amount of endogenous degrading microorganisms. Furthermore, the production of inoculum for application in bioaugmentation using low-cost substrates, such as industrial waste, would lead to the development of an environmentally friendly and attractive process in terms of cost-benefit.

Bacterial Biodegradation of Perfluorooctanoic Acid (PFOA) and Perfluorosulfonic Acid (PFOS) Using Pure Pseudomonas Strains

The principal objective of the present research involved the achievement of high biodegradation degrees of perfluorooctanoic acid (PFOA) and perfluorosulfonic acid (PFOS) using pure individual bacterial strains. The use of such microorganisms can contribute to the improvement of the wastewater treatment process in sewage treatment plants through bioaugmentation or other bioremediation processes. Thus, in this study, we investigated the biodegradation potential of PFOA and PFOS. Bacterial strains tested in this study were from the Pseudomonas genus, namely: Pseudomonas aeruginosa and Pseudomonas putida, due to their known capacity to degrade xenobiotic compounds. The results indicated that Pseudomonas aeruginosa was able to transform 27.9% of PFOA and 47.3% of PFOS in 96 h, while Pseudomonas putida managed to transform 19.0% of PFOA and 46.9% of PFOS in the same time frame. During the biodegradation tests, PFHxA was recognized as the principal biotransformation product of PFOA in the presence of Pseudomonas aeruginosa, and PFPeA, PFPxA and PFHpA were recognized as the biotransformation products in the presence of Pseudomonas putida. For PFOS, only two biotransformation products (PHHxA and PFHpA) were observed as a consequence of biodegradation by both bacterial strains.

Autochthonous psychrophilic hydrocarbonoclastic bacteria and its ecological function in contaminated cold environments.

Petroleum hydrocarbon (PH) pollution has mostly been caused by oil exploration, extraction, and transportation activities in colder regions, particularly in the Arctic and Antarctic regions, where it serves as a primary source of energy. Due to the resilience feature of nature, such polluted environments become the realized ecological niches for a wide community of psychrophilic hydrocarbonoclastic bacteria (PHcB). In contrast, to other psychrophilic species, PHcB is extremely cold-adapted and has unique characteristics that allow them to thrive in greater parts of the cold environment burdened with PHs. The stated group of bacteria in its ecological niche aids in the breakdown of litter, turnover of nutrients, cycling of carbon and nutrients, and bioremediation. Although such bacteria are the pioneers of harsh colder environments, their growth and distribution remain under the influence of various biotic and abiotic factors of the environment. The review discusses the prevalence of PHcB community in colder habitats, the metabolic processes involved in the biodegradation of PH, and the influence of biotic and abiotic stress factors. The existing understanding of the PH metabolism by PHcB offers confirmation of excellent enzymatic proficiency with high cold stability. The discovery of more flexible PH degrading strategies used by PHcB in colder environments could have a significant beneficial outcome on existing bioremediation technologies. Still, PHcB is least explored for other industrial and biotechnological applications as compared to non-PHcB psychrophiles. The present review highlights the pros and cons of the existing bioremediation technologies as well as the potential of different bioaugmentation processes for the effective removal of PH from the contaminated cold environment. Such research will not only serve to investigate the effects of pollution on the basic functional relationships that form the cold ecosystem but also to assess the efficacy of various remediation solutions for diverse settings and climatic conditions.

Bioaugmentation and phytoremediation wastewater treatment process as a viable alternative for pesticides removal: case of pentachlorophenol.

The online version contains supplementary material available at 10.1007/s40201-023-00865-y.

Recent trends in polycyclic aromatic hydrocarbons pollution distribution and counteracting bio-remediation strategies

Polycyclic aromatic hydrocarbons (PAHs) are distributed worldwide due to long-term anthropogenic pollution sources. PAHs are recalcitrant and highly persistent in the environment due to their inherent properties, such as heterocyclic aromatic ring structures, thermostability, and hydrophobicity. They are highly toxic, carcinogenic, immunotoxic, teratogenic, and mutagenic to various life systems. This review focuses on the unique data of PAH sources, exposure routes, detection techniques, and harmful effects on the environment and human health. This review provides a comprehensive and systematic compilation of eco-friendly biological treatment solutions for PAH remediation, such as microbial remediation approaches utilizing microbial cultures. In situ and Ex situ bioremediation of PAH methods, including composting land farming, biopiles, bioreactors bioaugmentation, and phytoremediation processes, are discussed in detail, as is a summary of the factors affecting and limiting PAH bioremediation. This review provides an overview of emerging technologies that use multi-process combinatorial treatment approaches and answers to generating value-added by-products during PAH remediation.

Remoción de materia orgánica presente en aguas residuales de una planta farmacéutica mediante un RBC (contactor biológico rotatorio)

A RBC (Rotating Biological Contactor) system is a technology using a biological process by which microorganisms present in wastewater arefixed to partially-submerged parallel rotating discs forming a biofilm through bioaugmentation processes. This technology allows for the removal of contaminating organic matter from the water improving treatment processes. In this research work, a laboratory-scale RBC composed of four discs submerged approximately 40 % in a volume of 1 l (0.001 m3) was used for the purpose of reducing high levels of COD and BOD contained in the wastewater of a pharmaceutical plant with the aid of two different microbial consortiums. An initial characterization of COD and BOD of the wastewater sample was carried out in order to compare with six samples obtained from the reactor in operation. A maximum COD removal of 2 560 mg O2/l was obtained which, although very high, is beyond of the permissible limits allowed by Colombian law ( ordinance 0631 of 2015) but is significant because it represents an efficient removal percentage of 99.67 % with respect to the values obtained at the initial characterization

Petroleum-Degrading Fungal Isolates for the Treatment of Soil Microcosms.

The main purpose of this study was to degrade total petroleum hydrocarbons (TPHs) from contaminated soil in batch microcosm reactors. Native soil fungi isolated from the same petroleum-polluted soil and ligninolytic fungal strains were screened and applied in the treatment of soil-contaminated microcosms in aerobic conditions. The bioaugmentation processes were carried out using selected hydrocarbonoclastic fungal strains in mono or co-cultures. Results demonstrated the petroleum-degrading potential of six fungal isolates, namely KBR1 and KBR8 (indigenous) and KBR1-1, KB4, KB2 and LB3 (exogenous). Based on the molecular and phylogenetic analysis, KBR1 and KB8 were identified as Aspergillus niger [MW699896] and tubingensis [MW699895], while KBR1-1, KB4, KB2 and LB3 were affiliated with the genera Syncephalastrum sp. [MZ817958], Paecilomyces formosus [MW699897], Fusarium chlamydosporum [MZ817957] and Coniochaeta sp. [MW699893], respectively. The highest rate of TPH degradation was recorded in soil microcosm treatments (SMT) after 60 days by inoculation with Paecilomyces formosus 97 ± 2.54%, followed by bioaugmentation with the native strain Aspergillus niger (92 ± 1.83%) and then by the fungal consortium (84 ± 2.21%). The statistical analysis of the results showed significant differences.

Enhancement of micropollutant biotransformation by adding manganese sand in constructed wetlands

Recent investigations have shown that the addition of manganese (Mn) sand to constructed wetlands (i.e., Mn-amended CWs) can improve the performance of organic micropollutants (MPs) removal. In addition to the direct oxidation and adsorption of Mn oxides, the indirect role of Mn oxides in MP biotransformation is crucial to the removal of MPs but has seldom been referred to. Herein, we constructed lab-scale CWs with or without the addition of natural Mn sand (∼35% Mn oxides) to decipher the influence of Mn oxides on the biotransformation of the six selected MPs which commonly existed in the wastewater. The experimental results showed that the addition of Mn sand to CWs can improve the removal of MPs (8.48% atrazine, 13.16% atenolol, and 6.27% sulfamethoxazole [pairwise Wilcoxon test p < 0.05]). Combining the detection of transformation products and metagenomic sequencing, we found that the enhanced removal of atrazine in the Mn-amended CWs was mainly due to the bioaugmented hydroxylation process. The enrichment of biotransformation-related genes and associated microbes of atenolol and sulfamethoxazole in Mn-amended CWs indicated that the addition of Mn sand to CWs can strengthen the biotransformation of MPs. Furthermore, we found that these MP-biodegrading microbes were widely present in the full-scale CWs. Overall, our research provides fundamental information and insights for further application of Mn-amended CWs in MP removal.

Pesticide removal by the bioaugmentation process in secondary treated wastewater

Abstract The work was focused on the effect of the bioaugmentation process on STWW contaminated by pentachlorophenol (PCP: 100 mg L−1) by Pseudomonas putida AE015451. The monitoring of bioaugmentation treatments was assessed by chloride content determination via high-performance liquid chromatography (HPLC), optical density (OD) for microbial biomass determination, and pyoverdine and biofilm production. The process of bioaugmentation by a PGPR Pseudomonas strain showed a high-efficiency removal rate of PCP (100 mg L−1). The contaminant decreased up to 92% after 168 h. The production of pyoverdine and the formation of bacterial biofilm by the strain Ps. putida AE015451 showed an important role in tolerating the toxicity of PCP by using it as a carbon source. The obtained result proved that the pyoverdine production and biofilm formation help the Pseudomonas bacteria to tolerate to the stressed condition as pesticide. Moreover, the co-existence of the iron and PCP molecule ameliorate its biodegradation.

Bioreactors and biophoton-driven biohydrogen production strategies

Given the current issues with global warming and rising greenhouse gas emissions, biohydrogen is a viable alternative fuel option. Technologies to produce biohydrogen include photo fermentation, dark fermentation, direct and indirect bio-photolysis, and two-stage fermentation. Biological hydrogen generation is a green and promising technique with mild reaction conditions and low energy consumption compared to thermochemical and electrochemical hydrogen generation. To optimize hydrogen gas output using this method, the activity of hydrogen-consuming bacteria should be restricted during the production stages of hydrogen and acetate to prevent or limit hydrogen consumption. Raw material costs, poor hydrogen evolution rates, and large-scale output are the main limitations in biological hydrogen generation systems. Organic wastes would be the most preferred target feedstock for hydrogen fermentation, aside from biodegradable wastes, due to their high amount and simultaneous waste treatment advantage. This study examined the three primary methods for converting waste into bio-hydrogen: microbial electrolysis cell, thermochemical gasification, and biological fermentation, from both a technological and environmental standpoint. The effectiveness and applicability of these bioprocesses in terms of aspects influencing processes and their constraints are discussed. Alternative options for improving process efficiency, like microbial electrolysis, bio-augmentation, and multiple process integration, are also considered for industrial-level applications. Biohydrogen generation might be further enhanced by optimization of operating conditions and adding vital nutrients and nanoparticles. Cost reduction and durability enhancement are the most significant hindrances to fuel-cell commercialization. This review summarizes the biohydrogen production pathways, the impact of used organic waste sources, and bacteria. The work also addresses the essential factors, benefits, and challenges.

Reducing nitrogen loss during kitchen waste composting using a bioaugmented mechanical process with low pH and enhanced ammonia assimilation

Exploring the regulation of nitrogen transformation in bioaugmented mechanical composting (BMC) process for rural kitchen waste (KW) is essential to avoid the “not-in-my-backyard” phenomenon caused by nitrogen loss. Herein, nitrogen transformation and loss in BMC versus conventional pile composting (CPC) of KW were compared. The results showed that the total nitrogen loss in the BMC was 6.87–39.32 % lower than that in the CPC. The main pathways to prevent nitrogen loss in the BMC were reducing NH3 by avoiding a sharp increase in pH followed by transforming the preserved NH4+-N into recalcitrant nitrogen reservoir via enhanced ammonia assimilation. The enriched thermophilic bacteria with mineralization capacities (e.g., Bacillus and Corynebacterium) during rapid dehydration and heating in the BMC accumulated organic acids and easy-to-use carbon sources, which could lead to lower pH and ammonia assimilation enhancement, respectively. This study provides new ideas for formulating low-cost nitrogen conservation strategies in decentralized KW composting.

Different phenanthrene degraders between free-cell mediated and biochar-immobilization assisted soil bioaugmentation as identified by RNA-based stable isotope probing (RNA-SIP)

Bioaugmentation (BA) is an effective approach to remove polycyclic aromatic hydrocarbons (PAHs) from contaminated soils, and biochar is frequently used to enhance PAH degradation performance. In this study, phenanthrene (PHE) degradation behavior and active degraders in a petroleum-contaminated soil were investigated and compared between free-cell mediated and biochar-immobilization assisted bioaugmentation. Biochar-immobilization assisted bioaugmentation (BA-IPB) introduced PHE degraders immobilized on biochar and effectively promoted PHE degradation, achieving higher PHE removal efficiencies within 24 h (~58 %) than free-cell mediated bioaugmentation (BA-FPB, ~39 %). Soil microbial community structure significantly changed in both BA-FPB and BA-IPB treatments. Through RNA-stable isotope probing (SIP), 14 and 11 bacterial lineages responsible for in situ PHE degradation were identified in BA-FPB and BA-IPB treatments, respectively. ASV_17 in BA-FPB treatment was Rhodococcus in the exogenous bacterial mixture; in contrast, none of exogenous bacteria were involved in PHE degradation in BA-IPB treatment. Methylobacterium (ASV_186), Xanthomonas (ASV_41), Kroppenstedtia (ASV_205), Scopulibacillus (ASV_243), Bautia (ASV_356), and Lactobacillus (ASV_376) were identified as PHE degraders for the first time. Our findings expanded the knowledge of the active PHE degraders and underlying mechanisms in bioaugmentation process, and suggested biochar-immobilization assisted bioaugmentation as a promising strategy for the bioremediation of PAH contaminated soils.

Use of nanobubble water bioaugmented anaerobically digested sludge for high-efficacy energy production from high-solids anaerobic digestion of corn straw

An increasing attention has been paid to the secure and sustainable management of agricultural wastes, especially lignocellulosic biomass. Nanobubble water (NBW) contains 106–108 bubbles/mL with diameter <1000 nm. Although previous studies have examined the enhancement effects of NBW on methane production from organic solid wastes, the NBW-based anaerobic digestion (AD) system is still restrained from practical application due to the large increase in AD reactor volume, generation of wastewater, and increase in energy consumption as well. In this study, NBW bioaugmentation of anaerobically digested sludge for the first time was performed for high-solids AD of corn straw. Results show that cellulase, xylanases and lignin peroxidase activities were increased by 2–55% during the NBW bioaugmentation process. Significant enrichment of hydrolytic/acidogenic bacteria and methanogenic archaea were noticed in the NBW bioaugmented sludge. This study clearly demonstrated 47% increase in methane production from high-solids AD of corn straw when O2-NBW bioaugmented sludge was applied, achieving a net energy gain of 5138 MJ/t-volatile solids of corn straw with an energy recovery of 34%. The NBW-based high-solids AD system can provide a novel and sustainable management solution for renewable energy production from agricultural wastes, targeting the reduction of environmental pollution and energy crisis.