Microbial Advances in a Sustainable Environment: Biological Waste Treatment and Bioconversion Technology

A special issue of Microorganisms (ISSN 2076-2607). This special issue belongs to the section "Microbial Biotechnology".

Deadline for manuscript submissions: closed (15 February 2023) | Viewed by 24640

Special Issue Editors


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Guest Editor
School of Environment, Harbin Institute of Technology, Harbin 150090, China
Interests: microbial diversity; sustainable environment; zero-waste approaches; biodegradation; bioenergy; multi-omics
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
School of Engineering, Northeast Agricultural University, Harbin 150030, China
Interests: co-fermentation; digester; biogas production

Special Issue Information

Dear Colleagues,

At present, environmental pollution has increased due to intensive anthropogenic activities along with the emergence of new materials that were previously not found in nature. The occurrence of emerging diverse contaminants along with the lack of in-depth information about microbial processes are major obstacles in the application of bioconversion approaches. There is an urgent need for more research to explore different ecosystems to 1) find microbes with potential activities, 2) understand microbial behavior in various environments (such as anaerobic digesters, fermenters, and waste treatments plants), 3) integrate various technologies to improve microbes’ productivity, and 4) mediate zero-waste approaches via microorganisms for sustainable environmental development.

In this Special Issue, we intend to gather recent research work and critical reviews in the field of environmental microbiology and bioenergy, especially on waste treatment during bioenergy production. Topics of interest include but are not limited to:

  • Screening potential microbes for waste treatment and bioenergy production;
  • Realizing microbial conversion of waste/biomass toward a zero-waste approach;
  • Enhancing fermentation processes via co-culturing, biostimulation, and technology innovation;
  • Applying novel molecular-based techniques, changes in microbial communities, and functional genomics and/or proteomics for improved bioenergy/bioproduct yield.

Dr. Guangli Cao
Prof. Dr. Yong Sun
Guest Editors

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Published Papers (10 papers)

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Research

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12 pages, 1327 KiB  
Article
Microbial Recycling of Polylactic Acid Food Packaging Waste into Carboxylates via Hydrolysis and Mixed-Culture Fermentation
by David P. B. T. B. Strik and Brian Heusschen
Microorganisms 2023, 11(8), 2103; https://doi.org/10.3390/microorganisms11082103 - 18 Aug 2023
Cited by 1 | Viewed by 2133
Abstract
To establish a circular economy, waste streams should be used as a resource to produce valuable products. Biodegradable plastic waste represents a potential feedstock to be microbially recycled via a carboxylate platform. Bioplastics such as polylactic acid food packaging waste (PLA-FPW) are theoretically [...] Read more.
To establish a circular economy, waste streams should be used as a resource to produce valuable products. Biodegradable plastic waste represents a potential feedstock to be microbially recycled via a carboxylate platform. Bioplastics such as polylactic acid food packaging waste (PLA-FPW) are theoretically suitable feedstocks for producing carboxylates. Once feasible, carboxylates such as acetate, n-butyrate, or n-caproate can be used for various applications like lubricants or building blocks for making new bioplastics. In this study, pieces of industrial compostable PLA-FPW material (at 30 or 60 g/L) were added to a watery medium with microbial growth nutrients. This broth was exposed to 70 °C for a pretreatment process to support the hydrolysis of PLA into lactic acid at a maximum rate of 3.0 g/L×d. After 21 days, the broths of the hydrolysis experiments were centrifugated and a part of the supernatant was extracted and prepared for anaerobic fermentation. The mixed microbial culture, originating from a food waste fermentation bioprocess, successfully fermented the hydrolyzed PLA into a spectrum of new C2-C6 multi-carbon carboxylates. n-butyrate was the major product for all fermentations and, on average, 6.5 g/L n-butyrate was obtained from 60 g/L PLA-FPW materials. The wide array of products were likely due to various microbial processes, including lactate conversion into acetate and propionate, as well as lactate-based chain elongation to produce medium-chain carboxylates. The fermentation process did not require pH control. Overall, we showed a proof-of-concept in using real bioplastic waste as feedstock to produce valuable C2-C6 carboxylates via microbial recycling. Full article
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18 pages, 4327 KiB  
Article
Microbial Synthesis of Lactic Acid from Cotton Stalk for Polylactic Acid Production
by Meenakshi Paswan, Sudipto Adhikary, Heba Hassan Salama, Alexandru Vasile Rusu, Antonio Zuorro, Bharatkumar Z. Dholakiya, Monica Trif and Sourish Bhattacharya
Microorganisms 2023, 11(8), 1931; https://doi.org/10.3390/microorganisms11081931 - 28 Jul 2023
Cited by 3 | Viewed by 1495
Abstract
Cotton stalk, a waste product in agriculture, serves as a beneficial, low-cost material as a medium for microbial synthesis of lactic acid as desired for polylactic acid synthesis. Cotton stalk was used as a substrate for microbial lactic acid synthesis, and a novel [...] Read more.
Cotton stalk, a waste product in agriculture, serves as a beneficial, low-cost material as a medium for microbial synthesis of lactic acid as desired for polylactic acid synthesis. Cotton stalk was used as a substrate for microbial lactic acid synthesis, and a novel strain of Lactococcus cremoris was reported to synthesize 51.4 g/L lactic acid using cellulose recovered from the cotton stalk. In total, 18 Lactobacillus isolates were isolated from kitchen waste, soil, sugarcane waste, and raw milk samples screened for maximum lactic acid production. It was found that one of the Lactococcus cremoris isolates was found to synthesize maximum lactic acid at a concentration of 51.4 g/L lactic acid in the hydrolysate prepared from cotton stalk. The upstream process parameters included 10% inoculum size, hydrolysate containing reducing sugars 74.23 g/L, temperature 37 °C, agitation 220 rpm, production age 24 h. Only the racemic (50:50) mixture of D-LA and L-LA (i.e., D/L-LA) is produced during the chemical synthesis of lactic acid, which is undesirable for the food, beverage, pharmaceutical, and biomedical industries because only the L-form is digestible and is not suitable for biopolymer, i.e., PLA-based industry where high optically purified lactic acid is required. Furthermore, polylactic acid was synthesized through direct polycondensation methods using various catalysts such as chitosan, YSZ, and Sb2O3. PLA is biocompatible and biodegradable in nature (its blends and biocomposites), supporting a low-carbon and circular bioeconomy. Full article
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13 pages, 2685 KiB  
Article
Improved Biohythane Production from Rice Straw in an Integrated Anaerobic Bioreactor under Thermophilic Conditions
by Lili Dong, Guangli Cao, Wanqing Wang, Geng Luo, Fei Yang and Nanqi Ren
Microorganisms 2023, 11(2), 474; https://doi.org/10.3390/microorganisms11020474 - 14 Feb 2023
Cited by 1 | Viewed by 1626
Abstract
This study evaluated the feasibility of continuous biohythane production from rice straw (RS) using an integrated anaerobic bioreactor (IABR) at thermophilic conditions. NaOH/Urea solution was employed as a pretreatment method to enhance and improve biohythane production. Results showed that the maximum specific biohythane [...] Read more.
This study evaluated the feasibility of continuous biohythane production from rice straw (RS) using an integrated anaerobic bioreactor (IABR) at thermophilic conditions. NaOH/Urea solution was employed as a pretreatment method to enhance and improve biohythane production. Results showed that the maximum specific biohythane yield was 612.5 mL/g VS, including 104.1 mL/g VS for H2 and 508.4 mL/g VS for CH4, which was 31.3% higher than the control RS operation stage. The maximum total chemical oxygen demand (COD) removal stabilized at about 86.8%. COD distribution results indicated that 2% of the total COD (in the feed) was converted into H2, 85.4% was converted to CH4, and 12.6% was retained in the effluent. Furthermore, carbon distribution analysis demonstrated that H2 production only diverted a small part of carbon, and most of the carbon flowed to the CH4 fermentation process. Upon further energy conversion analysis, the maximum value was 166.7%, 31.7 times and 12.8% higher than a single H2 and CH4 production process. This study provides a new perspective on lignocellulose-to-biofuel recovery. Full article
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16 pages, 2020 KiB  
Article
Promoting the Circular Economy on an Island: Anaerobic Co-Digestion of Local Organic Substrates as a Possible Renewable Energy Source
by Juana Fernández-Rodríguez, Mónica Di Berardino and Santino Di Berardino
Microorganisms 2023, 11(2), 285; https://doi.org/10.3390/microorganisms11020285 - 21 Jan 2023
Cited by 3 | Viewed by 1528
Abstract
The local waste co-digestion is an interesting option to tackle in reduced and isolated areas like the islands. The islands have limited territory and scarce fuel production. Moreover, organic waste can create serious environmental problems in soil, water and air. Anaerobic co-digestion (AcoD) [...] Read more.
The local waste co-digestion is an interesting option to tackle in reduced and isolated areas like the islands. The islands have limited territory and scarce fuel production. Moreover, organic waste can create serious environmental problems in soil, water and air. Anaerobic co-digestion (AcoD) is a technology fulfilling the concept of waste-to-energy (WtE) based on local resources. The valorisation of organic waste through AcoD on an island would prevent environmental impacts, while being a source of renewable energy. In this study, cow manure (outdoor and indoor), pig slurry, bird manure, kitchen waste, sewage sludge and oily lacteous waste produced on Island Terceira (Portugal) were tested in mesophilic −35 °C- Biochemical Methane Potential (BMP) co-digestion assays. The goals were to analyse the recalcitrant and high potential produced waste and to estimate the energetic supply source on the island. The cow manure and pig slurry were used as inocula and specific methanogenic activities (SMAs) were carried out. The results showed that both substrates have a significant methanogenic activity–SMA 0.11 g-COD/(g-VSS.d) and 0.085 g-COD/(g-VSS.d), respectively. All the studied combinations were feasible in AcoD, showing TS removals in the range of 19–37%; COD removals in the range 67–78% and specific methane yields from 0.14 to 0.22 L/gCOD removed, but some differences were found. The modified Gompertz model fitted the AcoD assays (R2 0.982–0.998). The maximum biogas production rate, Rmax. was highest in the AcoD of Cow+Pig+Oily and in the Cow+Pig+Sludge with 0.017 and 0.014 L/g-VSadded.day, respectively, and the lowest in Cow+Pig+Bird with 0.010 L/g-VSadded. In our AcoD studies, the bird manure limited the performance of the process, since it was recalcitrant to anaerobic degradation. On the other hand, the oily lacteous waste showed a great potential in the anaerobic digestion. The estimated biogas production, from the best-studied condition, could cover the 11.4% of the energy supply of the inhabitants. These preliminary results would prevent the environmental impact of organic waste on the island and promote the use of local waste in a circular economy scenario. Full article
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20 pages, 5740 KiB  
Article
Removal of Hydrogen Sulfide from Swine-Waste Biogas on a Pilot Scale Using Immobilized Paracoccus versutus CM1
by Ladapa Kumdhitiahutsawakul, Dolruedee Jirachaisakdeacha, Uthen Kantha, Patiroop Pholchan, Pachara Sattayawat, Thararat Chitov, Yingmanee Tragoolpua and Sakunnee Bovonsombut
Microorganisms 2022, 10(11), 2148; https://doi.org/10.3390/microorganisms10112148 - 29 Oct 2022
Cited by 4 | Viewed by 1488
Abstract
Hydrogen sulfide (H2S) is a toxic and corrosive component that commonly occurs in biogas. In this study, H2S removal from swine-waste biogas using sulfur-oxidizing Paracoccus versutus CM1 immobilized in porous glass (PG) and polyurethane foam (PUF) biofilters was investigated. [...] Read more.
Hydrogen sulfide (H2S) is a toxic and corrosive component that commonly occurs in biogas. In this study, H2S removal from swine-waste biogas using sulfur-oxidizing Paracoccus versutus CM1 immobilized in porous glass (PG) and polyurethane foam (PUF) biofilters was investigated. Bacterial compositions in the biofilters were also determined using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). The biofilters were first tested on a laboratory scale under three space velocities (SV): 20, 30, and 40 h−1. Within 24 h, at an SV of 20 h−1, PG and PUF biofilters immobilized with P. versutus CM1 removed 99.5% and 99.7% of H2S, respectively, corresponding to the elimination capacities (EC) of 83.5 and 86.2 gm−3 h−1. On a pilot scale, with the horizontal PG-P. versutus CM1 biofilter operated at an SV of 30 h−1, a removal efficiency of 99.7% and a maximum EC of 113.7 gm−3 h−1 were achieved. No reduction in methane content in the outlet biogas was observed under these conditions. The PCR-DGGE analysis revealed that Paracoccus, Acidithiobacillus, and Thiomonas were the predominant bacterial genera in the biofilters, which might play important roles in H2S removal. This PG–P. versutus CM1 biofiltration system is highly efficient for H2S removal from swine-waste biogas. Full article
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17 pages, 2905 KiB  
Article
Application of Aspergillus niger in Practical Biotechnology of Industrial Recovery of Potato Starch By-Products and Its Flocculation Characteristics
by Liang Zhang, Guangli Cao, He Liu, Zhenting Wu, Dianliang Gong, Xin Ru, Xiujie Gong, Qiuyue Pi and Qian Yang
Microorganisms 2022, 10(9), 1847; https://doi.org/10.3390/microorganisms10091847 - 15 Sep 2022
Cited by 3 | Viewed by 2079
Abstract
This study developed a practical recovery for potato starch by-products by A. niger and applied it on a plant scale to completely solve the pollution problems. Soughing to evaluate the effect of A. niger applied towards the production of by-products recycling and analyze [...] Read more.
This study developed a practical recovery for potato starch by-products by A. niger and applied it on a plant scale to completely solve the pollution problems. Soughing to evaluate the effect of A. niger applied towards the production of by-products recycling and analyze the composition and characteristics of flocculating substances (FS) by A. niger and advance a possible flocculation mechanism for by-product conversion. After fermentation, the chemical oxygen demand (COD) removal rate, and the conversion rates of cellulose, hemicellulose, pectin, and proteins were 58.85%, 40.19%, 53.29%, 50.14%, and 37.09%, respectively. FS was predominantly composed of proteins (45.55%, w/w) and polysaccharides (28.07%, w/w), with two molecular weight distributions of 7.3792 × 106 Da and 1.7741 × 106 Da and temperature sensitivity. Flocculation was mainly through bridging and ionic bonding, furthermore, sweeping effects may occur during sediment. Flocculation was related to by-products conversion. However, due to severe pollution problems and resource waste, and deficiencies of existing recovery technologies, converting potato starch by-products via A. niger liquid fermentation merits significant consideration. Full article
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18 pages, 25233 KiB  
Article
High Potential Decolourisation of Textile Dyes from Wastewater by Manganese Peroxidase Production of Newly Immobilised Trametes hirsuta PW17-41 and FTIR Analysis
by Bancha Thampraphaphon, Cherdchai Phosri, Nipon Pisutpaisal, Pisit Thamvithayakorn, Kruawan Chotelersak, Sarper Sarp and Nuttika Suwannasai
Microorganisms 2022, 10(5), 992; https://doi.org/10.3390/microorganisms10050992 - 9 May 2022
Cited by 9 | Viewed by 2256
Abstract
Coloured wastewater from the textile industry is a very serious global problem. Among 16 different white-rot fungal isolates, Trametes hirsuta PW17-41 revealed high potential for decolourisation of mixed textile dyes (Navy EC-R, Ruby S3B and Super Black G) from real industrial wastewater samples. [...] Read more.
Coloured wastewater from the textile industry is a very serious global problem. Among 16 different white-rot fungal isolates, Trametes hirsuta PW17-41 revealed high potential for decolourisation of mixed textile dyes (Navy EC-R, Ruby S3B and Super Black G) from real industrial wastewater samples. The efficiency of dye decolourisation was evaluated using the American Dye Manufacturers’ Institute (ADMI) standard methodology. The suitable support for fungal mycelium immobilisation was nylon sponges. The optimal dye decolourisation (95.39%) was achieved by using palm sugar and ammonium nitrate as carbon and nitrogen sources, respectively. The initial pH was 5 and the agitation speed was 100 rpm at 30 °C. The ADMI values of textile dyes decreased from 2475 to 114 within two days, reducing the treatment time from seven days before optimisation. The major mechanism of dye decolourisation was biodegradation, which was confirmed by UV–visible and FTIR spectra. Manganese peroxidase (MnP) (4942 U L−1) was found to be the main enzyme during the decolourisation process at an initial dye concentration of 21,200 ADMI. The results indicated the strong potential of immobilised fungal cells to remove high concentrations of textile dyes from industrial wastewater and their potential ability to produce high MnP and laccase activities that can be used in further application. Full article
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Review

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13 pages, 766 KiB  
Review
Current Trends in Bioaugmentation Tools for Bioremediation: A Critical Review of Advances and Knowledge Gaps
by Olga Muter
Microorganisms 2023, 11(3), 710; https://doi.org/10.3390/microorganisms11030710 - 9 Mar 2023
Cited by 12 | Viewed by 5650
Abstract
Bioaugmentation is widely used in soil bioremediation, wastewater treatment, and air biofiltration. The addition of microbial biomass to contaminated areas can considerably improve their biodegradation performance. Nevertheless, analyses of large data sets on the topic available in literature do not provide a comprehensive [...] Read more.
Bioaugmentation is widely used in soil bioremediation, wastewater treatment, and air biofiltration. The addition of microbial biomass to contaminated areas can considerably improve their biodegradation performance. Nevertheless, analyses of large data sets on the topic available in literature do not provide a comprehensive view of the mechanisms responsible for inoculum-assisted stimulation. On the one hand, there is no universal mechanism of bioaugmentation for a broad spectrum of environmental conditions, contaminants, and technology operation concepts. On the other hand, further analyses of bioaugmentation outcomes under laboratory conditions and in the field will strengthen the theoretical basis for a better prediction of bioremediation processes under certain conditions. This review focuses on the following aspects: (i) choosing the source of microorganisms and the isolation procedure; (ii) preparation of the inoculum, e.g., cultivation of single strains or consortia, adaptation; (iii) application of immobilised cells; (iv) application schemes for soil, water bodies, bioreactors, and hydroponics; and (v) microbial succession and biodiversity. Reviews of recent scientific papers dating mostly from 2022–2023, as well as our own long-term studies, are provided here. Full article
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26 pages, 2768 KiB  
Review
A Review of Biogenic Coalbed Methane Experimental Studies in China
by Run Chen, Yunxia Bao and Yajun Zhang
Microorganisms 2023, 11(2), 304; https://doi.org/10.3390/microorganisms11020304 - 24 Jan 2023
Cited by 2 | Viewed by 1871
Abstract
Biogenic coalbed methane (CBM) is an important alternative energy that can help achieve carbon neutrality. Accordingly, its exploration and development have become a research hotspot in the field of fossil energy. In this review, the latest detection technologies for and experimental research on [...] Read more.
Biogenic coalbed methane (CBM) is an important alternative energy that can help achieve carbon neutrality. Accordingly, its exploration and development have become a research hotspot in the field of fossil energy. In this review, the latest detection technologies for and experimental research on biogenic CBM in China in recent decades are summarized. The factors influencing the generation of biogenic CBM and the identification method of biogenic CBM are systematically analyzed. The technologies to detect biogas and the research methods to study microbial diversity are summarized. The literature shows that biogenic CBM is easily produced in the presence of highly abundant organic matter of low maturity, and the organic matter reaching a certain thickness can compensate for the limitation of biogenic CBM gas production due to the small abundance of organic matter to a certain extent. Biogenic CBM production could be increased in an environment with low salinity, medium alkalinity, and rich Fe2+ and Ni2+ sources. Furthermore, biogenic CBM can be identified by considering three aspects: (1) the presence of gas composition indicators; (2) the content of heavy hydrocarbon; and (3) variation in the abundance of biomarkers. In recent years, research methods to study the microbial community and diversity of CBM-producing environments in China have mainly included 16S rRNA gene library, fluorescence in situ hybridization, and high-throughput sequencing, and the dominant microorganisms have been determined in various basins in China. The results of numerous studies show that the dominant bacterial phyla are commonly Firmicutes and Proteobacteria, while the archaeal fraction mainly includes Methanoculleus, Methanobacterium, Methanocorpusculum, and Methanothrix. This review summarizes and discusses the advances in biogenic CBM production and the associated microbial community in order to promote further development of coal biotransformation and CO2 bio-utilization to meet energy demands under carbon neutrality. Full article
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20 pages, 2017 KiB  
Review
Recent Advances in Micro-/Nanoplastic (MNPs) Removal by Microalgae and Possible Integrated Routes of Energy Recovery
by Abdelfatah Abomohra and Dieter Hanelt
Microorganisms 2022, 10(12), 2400; https://doi.org/10.3390/microorganisms10122400 - 3 Dec 2022
Cited by 14 | Viewed by 3065
Abstract
Reliance on plastic has resulted in the widespread occurrence of micro-/nanoplastics (MNPs) in aquatic ecosystems, threatening the food web and whole ecosystem functions. There is a tight interaction between MNPs and microalgae, as dominant living organisms and fundamental constituents at the base of [...] Read more.
Reliance on plastic has resulted in the widespread occurrence of micro-/nanoplastics (MNPs) in aquatic ecosystems, threatening the food web and whole ecosystem functions. There is a tight interaction between MNPs and microalgae, as dominant living organisms and fundamental constituents at the base of the aquatic food web. Therefore, it is crucial to better understand the mechanisms underlying the interactions between plastic particles and microalgae, as well as the role of microalgae in removing MNPs from aquatic ecosystems. In addition, finding a suitable route for further utilization of MNP-contaminated algal biomass is of great importance. The present review article provides an interdisciplinary approach to elucidate microalgae–MNP interactions and subsequent impacts on microalgal physiology. The degradation of plastic in the environment and differences between micro- and nanoplastics are discussed. The possible toxic effects of MNPs on microalgal growth, photosynthetic activity, and morphology, due to physical or chemical interactions, are evaluated. In addition, the potential role of MNPs in microalgae cultivation and/or harvesting, together with further safe routes for biomass utilization in biofuel production, are suggested. Overall, the current article represents a state-of-the-art overview of MNP generation and the consequences of their accumulation in the environment, providing new insights into microalgae integrated routes of plastic removal and bioenergy production. Full article
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