The demand for ecologically cultivated fruits is growing each year, but the yields in organic farming are still lower than the yields in conventional farming. Moreover plant pathogens are a serious threat in organic fruit production and the assortment of conventional pesticides is limited in organic farming. The European Commission has established regulations that state which types of bioproducts can be used in organic farming. Appropriately chosen biopreparations might be a solution to this problem. Biopreparations are products used to inhibit the growth of pathogenic fungi or bacteria, stimulate plants growth and enhance plant nutrient uptake. They can be composed of plant growth promoting bacteria and fungi, plant extracts or animals-derived compounds. The second category of bioproducts useful for enhancing yield and nutrient uptake are biostimulants. They can be composed of microorganisms, protein hydrolysates, seaweed extracts and other substances. Bacteria, fungi and yeasts are used in biocontrol of plant pathogens and in enhancing plants growth by producing hormone-like substances and reducing symptoms of environmental stress caused by weather or soil factors such as drought or low nutrient availability.

Aquaculture ponds are simple and unique ecosystems, which are affected intensively by human activities. In this mini-review, we focus our attention on the distribution and community diversity of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) in pond water and sediments, as well as the possible ecological mechanisms involved. Moreover, we discuss the possibility of increasing the activity of ammonia-oxidizing organisms in order to improve the water quality in aquaculture ponds. Compared with eutrophic lakes, the significantly higher ammonia concentration in pond water does not lead to significantly higher AOB levels, and the abundance of AOA is too low to quantify accurately. Similar to eutrophic lakes, high abundances of AOA and AOB are present in the surface sediments at the same time, where the oxidation of ammonia is performed mainly by AOB. AOB and AOA exhibit significant seasonal variations in aquaculture ponds, which are affected by the temperature, pH, and dissolved oxygen. The dominant AOB species are Nitrosomonas and the Nitrosospira lineage in pond environments. Nitrososphaera or members of the Nitrososphaera-like cluster dominate the AOA species in surface sediments, whereas the Nitrosopumilus cluster dominates the deeper sediments. AOB and AOA can be enriched on artificial substrates suspended in the pond water, thereby potentially improving the water quality.

One of the major concerns faced by the iron and steel industry, other than the abundant emission of carbon dioxide into the atmosphere, is the huge quantity of slag that is generated during the manufacturing of iron and steel. A comprehensive understanding of the iron and steel slag properties has diverted them away from stockpiling or landfilling to useful engineering applications. The similarity of these slags to natural minerals used in geologic carbon dioxide sequestration has made them sustainable alternative for industrial-scale carbon capture and storage. Further, they possess properties that are conducive for remediation of soil and groundwater contaminated with heavy metals and other toxic chemicals. This paper reviews the iron and steel slag characteristics suitable for engineering applications, describes several engineering application examples, and discusses challenges and opportunities to develop practical applications using iron and steel slags. This paper also discusses the on-going research which explores the use of steel slag along with the biochar-amended soil to develop a biogeochemical landfill cover to sequester fugitive gas emissions such as CH₄, CO₂ and H₂S from MSW landfills and attain zero-emissions landfill.

Anaerobic digestion is a versatile biotechnology to treat waste activated sludge (WAS), the main by-products of biological wastewater treatment, because it can achieve simultaneously energy recovery (biogas) and pollutant reduction (organic matter, pathogens). However, the potential of biogas production from mono-digestion of WAS is usually limited by the imbalance carbon to nitrogen (C/N) ratio of WAS and ammonia accumulation. Anaerobic co-digestion, simultaneous digestion of two or more substrates, should be a feasible option to resolve these disadvantages. The abundant organic wastes from municipal, industrial, and agricultural field have been the ideal co-substrates because they not only can balance the substrate nutrient to obtain the optimal C/N ratio, but also can adjust pH and dilute the toxic materials to mitigate the inhibition to methanogens, consequently improving the yield of biogas, especially methane. This paper classified the main organic co-substrates according to their source and reviewed their application in anaerobic co-digestion of WAS. Then the influence of temperature, pH, organic loading rate, hydraulic retention time, C/N ratio, digester type and pretreatment method on biogas production was extensively discussed. Finally, this review brought forward the challenges and outlooks of anaerobic co-digestion in the future.

The depletion of conventional energy sources has motivated countries to shift towards renewable and eco-friendly sources of energy. One of the major global energy consumers is wastewater treatment facilities, particularly biological processes. The microbial fuel cell (MFC) is an emerging biotechnology that has been proven to be able to treat a wide range of wastewaters while generating electricity. However, after two decades of extensive research, the MFC technology remains mostly trapped in laboratory experimentations studying its performance and potential improvements. Moving towards the commercialization of MFC technology, multiple studies have focused on its actual performance under realistic conditions, i.e., large-scale continuous operation. Scaling up MFCs has been tested by increasing the unit size, stacking individual cells, and/or using multiple electrodes. As more research had been carried out in this area, the aim of the present article is to review the various designs and configurations of continuous scaled-up experiments from treatment, power generation, and applicability perspectives. This review compiles more than one hundred research studies on continuous scalable MFCs. The key operation parameters, including the hydraulic retention time and organic loading rate, are thoroughly discussed to obtain practical optimum ranges in comparison to conventional treatment processes. The various scaled-up cell materials and configurations are analyzed and correlated to their reported performance. Design guidelines for process variables and system components/configurations are suggested, and relevant research gaps and challenges are identified.

Biofuel research and development roadmap is currently underway in several countries and is expected to pave a way for the establishment of a viable renewable energy sector that can compete with petroleum-based fuels. Ethanol fermentation has garnered increasing attention amongst various stakeholders (industries, governments, and academia) due to its economic and environmental merits. However, microbial contamination continues to be one of the major barriers in ethanologenic processes, resulting in low ethanol yields and thereby translating into economic losses. To this end, technological innovations geared towards effective elimination of microbial contamination are constantly being developed. This review explores and discusses the fermentation conditions that facilitate the growth of undesired microorganisms during ethanol fermentation processes. It highlights the methods that are currently used in biorefineries as well as innovative and advanced biotechnological methods currently being evaluated as viable alternative strategies to control or eliminate microbial contaminants in ethanol fermentations. These methods have the potential to minimize or control the contamination problem and could pave a way for the development of an efficient biofuel sector.

Due to their large-scale manufacture and widespread application, there have been a number of studies related to toxicological assessment of nanomaterials (NMs) over the past decade. Although there has been extensive research on the cytotoxicity of NMs, concerns have been raised about their possible genotoxicity. The genome is constantly exposed to genotoxic insults that can lead to DNA damage, which in turn can have consequences for health, such as the induction of carcinogenesis. This comprehensive review focuses on the direct and indirect interactions of NMs with DNA. Factors influencing the genotoxicity of NMs, such as their physicochemical characteristics, are also discussed. The mechanisms involved in the direct and indirect interactions of NMs with DNA are also reviewed. Many studies have shown that ENMs have genotoxic effects, such as chromosomal fragmentation, DNA strand breaks, point mutations, oxidative DNA adducts, apoptosis, hypoxic responses, mitochondrial dysfunction, and epigenetic modifications. As the data reported to date are inconsistent, it is difficult to draw definitive conclusions regarding the features of NMs that promote genotoxicity. Therefore, challenges and future research perspectives are discussed. This review provides insights into the genotoxic effects of NMs and their consequences for human health.

Microorganisms are responsible for the conversion and breakdown of organic compounds and contaminants in bioreactors designed for the treatment of different types of waste. Organized in highly complex communities, they are the heart of every wastewater treatment plant and solid residue landfill. The detailed characterization of these communities and their taxonomic classification based on phylogenetic data are of great utility in monitoring the responses of the system to changing operational parameters and the development and optimization of favorable conditions within the bioreactors these communities inhabit. Until recently, only a fraction of the microbial diversity could be assessed, limited by the available sequencing technology, which was not suited for a high-throughput implementation. With the introduction of the recent next-generation sequencing (NGS) methods, an enormous advance has taken place allowing researchers in microbial ecology to generate large amounts of phylogenetic data in a short time and at relatively low costs. In this review, we present and discuss how the increase in available information has influenced recent research and the results available phylogenetic data has produced in the field of wastewater treatment. Furthermore, we introduce the data processing of NGS-based experiments, which has become more complex as the millions of sequences that a single sample can yield require the effective use of computational resources and human bioinformatics skills. To address this part of modern microbial ecology, the most popular sequencing techniques, as well as data analysis workflows, are outlined in this review article.

In the last few years, ecofriendly malic acid production has received a potential platform for the bio-based chemicals to replace the dependency of fossil based resources. The main goal of this paper is to explore the feasibility of efficient production of malic acid from cost effective alternative renewable byproducts as feedstock. To replace the traditional method of malic acid production from petroleum-based compounds such as maleic acid, the efficiency of fermentation technology for malic acid production using various microorganisms has been improved. To date, glucose is designated as the best substrate for malic acid production. However, few reviews concerning about malic acid production by employing various microbial strains were reported. The current knowledge on the biosynthesis of malic acid has assisted to improve malic acid production using various microbial strains. But, there is still need for the continuous production and replacement of low-cost substrates to increase the yield of malic acid. This review provides an overview about progress, achievements, merits, challenges and future perspectives in malic acid production from cost effective alternative substrates. Thus, malic acid production can be economical using renewable byproducts like crude glycerol by employing appropriate microorganism.

Furfural, which is directly derived from the hemicellulosic parts of lignocellulosic biomass, is considered as one of the most promising platform chemicals to manufacture commodity chemical products such as polymers and their monomers. Its production has already been commercialized. In this review, potentially relevant methods for producing important chemicals from furfural, which are used as monomers for different polymers, and for the polymerization of furfural and its derivatives (e.g., furfuryl alcohol), have been discussed. First, the production of furfural from different lignocellulosic biomasses is presented. Next, the synthesis of various monomers and their highest available yields from furfural are discussed. The polymers that can be directly produced from furfural and its derivatives are explored. Finally, the challenges of producing furfural-based products have been highlighted.