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The application of microalgae biotechnology, which can recover nutrients from wastewater, improve water quality, and feed some aquatic animals, is becoming an emerging trend in the development of eco‐friendly aquaculture. Previous studies explored a variety of models to support the use of microalgae in aquaculture practice, verifying the feasibility and advantages of microalgae‐based aquaculture. However, a couple of bottlenecks and problems jeopardizing the application of microalgae biotechnology in aquaculture are discovered in the research and industrial practice. This work, hence, summarizes the research progress and the current opinions relating with the microalgae‐based aquaculture and proposes some critical thoughts about the bottlenecks challenging its industrial implementation. © 2020 Society of Chemical Industry (SCI)

BACKGROUND: Microalgae biotechnology is considered as a promising way to recover nutrients from centrate wastewater for value‐added biomass production, but it is rarely adopted in a real‐world application. Current study confirmed that carbon deficiency and suspended solids are two problems jeopardizing the microalgae‐based wastewater remediation. In this regard, glycerol was added into centrate wastewater as exogenous carbon source and algal–bacterial cooperation for nutrients recovery assessment. RESULTS: The results showed that glycerol addition increased the biomass yield of algae from 1.54 to 2.58 g L⁻¹ in 5‐day culture and, at the same time, improved the removal efficiency of nitrogen and phosphorus, which were further assessed by pilot‐scale experiments. Bacterial community analysis indicated that algal–bacterial cooperation involves carbon dioxide and oxygen exchange, phosphorus absorption, and solid organics degradation, forming a complementary nexus beneficial for wastewater treatment. CONCLUSION: Glycerol is proven to be a good carbon source for microalgae growth in the centrate wastewater. Additionally, the cooperation between microalgae and bacteria plays a key role in the nutrients removal during centrate wastewater. It is expected the technology and knowledge provided by current work can further promote the industrialization of microalgae‐based wastewater remediation. © 2020 Society of Chemical Industry

Vermicomposting is a resource technology for managing animal excreta, whereas the internal relationships of the process are vital for its wide applications. The present study examined how macronutrient and micronutrient concentrations, microbial communities, and enzymatic activity of pig manure (PM) changed during the composting and vermicomposting processes and their internal interactions. The vermicomposting process increased macronutrients more significantly than composting (32.40% of total available nitrogen, 21.70% of total available phosphorous, and 12.70% of total available potassium). The vermicomposting reduced total organic carbon (7.91%), C/N ratio (61.35%), and humification index (56.47%) more than composting due to the quick decomposition of PM. After continual fertility optimization, the total microbial population, with the exception of total fungi, rose significantly to accelerate organics mineralization and improve macronutrients in vermicomposting compared to composting. Moreover, earthworm addition favored the stabilization of the PM containing higher concentrations of micronutrients after being catalyzed by the enhanced catalase activity and reduced sucrase activity after 90 days of vermicomposting. Principal component analysis and chord plots found that the generated vermicomposting products had higher fertility properties and biological activities induced by the synergistic effect of microorganisms and earthworms. These findings highlight vermicomposting is an eco-friendly management technology for processing PM and can be scaled up for agricultural applications.

Aquaponics is considered as a possible method to produce aquatic animals and plants in an environmentally‐friendly way, but its commercialization is seriously hindered owing to some technical and economic problems. Recently, the integration of microbial community with aquaponics is on the way to becoming the next‐generation technology for the sustainable development and commercialization of the aquaponics industry. This article provides an authoritative discussion on the novel microbial community‐assisted aquaponics, which will be emerging from the research environment to industrial application in the coming future. Principles and key technologies of this novel aquaponics, as well as the potential challenges to its commercialization, are discussed. It is expected that the emerging technologies discussed in this work could address the existed technical problems and further promote the commercialization of aquaponics. © 2019 Society of Chemical Industry

The identification of phosphate-accumulating organisms (PAOs), denitrifying phosphate-accumulating organisms (DPAOs) and their relationship is a key pathway for optimizing nitrate and phosphate removal efficiency in activated sludge. In this study, the acclimatization of microorganisms in sequencing batch reactor were performed with anaerobic/aerobic (A/O) and anaerobic/anoxic (A/A) cycles, the biomass changes of PAOs and DPAOs and the correlations were then discussed. The results indicated that after acclimatization, the nutrient removal efficiencies reached to 85.34% (COD), 93.64% (PO43--P) and 92.34% (NO3--N), respectively, with NO3--N:PO43-P of 1.5:1. The successful enrichment of PAOs and DPAOs (reached 97.9%) was verified by the change of relative metabolic activities, which was further proved by the change of bacterial diversity. The number of Candidatus Accumulibacter, Zoogloea, and Dechloromonas all increased at A/O and A/A stages while the number of Acinetobacter only increased at A/O stage. So Accumulibacter sp. was DPAO while Acinetobacter sp. was only PAO in this process, and genera Accumulibacter, Dechloromonas and Zoogloea greatly coordinated in denitrification and accumulating phosphorous though RDA and chord plot. This was worthy of attention and development to explore enhanced biological phosphorus removal (EBPR) in practical wastewater treatment via improving identification of bacterial species and symbiosis of bacteria community.

With the continuous development of the livestock breeding industry, the amount of piggery wastewater discharged increases year by year, and the pressure of controlling environmental pollution continuously increases. A novel method using a co-culture of Chlorella pyrenoidosa and Rhodotorula glutinis in piggery wastewater was proposed in this study, which was aimed at treating piggery wastewater and producing useful products. The results showed that the optimal inoculum ratio of algae to yeast was 3 : 1 in the wastewater, which achieved the removal efficiencies of 58.53%, 36.07%, 33.20% and 56.25% for ammoniacal nitrogen (NH3-N), total nitrogen (TN), total protein (TP) and chemical oxygen demand (COD), respectively, after 6 d. The synergistic relationship of C. pyrenoidosa and R. glutinis was preliminarily validated using the oxygen/carbon dioxide exchange balance and scanning electron microscopy images. The co-cultivation system gained 59.8% (w/w) protein within 5 d which can be used as a feed additive, and produces aquatic animals with better growth and quality. Thus, the 1000 litre pilot scale bioreactor was used indoors and removed 82.65% of TN, 53.51% of TP, 93.48% of NH3-N and 85.44% of COD in 21 d which gave a better performance for TN (p < 0.05) than the bench scale results. This system improves the nutrition removal and protein production efficiencies, and is a promising method for piggery wastewater treatment and the pig breeding industry.

The high concentrations of ions and ammonia nitrogen (NH3−N) in soil washing wastewater can remarkably affect ecosystem balance. This study aims to prove the feasibility of using alkaline soil washing wastewater as inlet water of microbial electrolysis desalination and chemical-production cell (MEDCC) to desalinate and recover NH3-N, from the views of performance and mechanism. The system could obtain desalination, and NH3-N removal efficiencies of 73 ± 7% and 85 ± 3%, respectively, within 12 h at the maximum current density of 9.8 ± 0.1 A/m2. Importantly, 82.5% of the removed NH3-N could be recovered in the form of NH3·H2O. The addition of electrochemically active bacteria in the anode chamber of MEDCC improved desalination and NH3-N recovery efficiencies by strengthing electric field. Bioenergy provided 58% of the total energy consumption, forming an energy-saving method for soil washing wastewater treatment. Alkalization pretreatment and acid immersion could reduce precipitation from membranes to improve desalination performance and reduce energy consumption. From the standpoint of the mechanism of desalination and NH3-N recovery, the MEDCC is expected to have the potential to simultaneously complete desalination and NH3-N recovery in alkaline wastewater with low energy consumption.

With the continuous development of the livestock breeding industry, the amount of piggery wastewater discharged increases year by year, and the pressure of controlling environmental pollution continuously increases. A novel method using a co-culture of

In recent years, as the algal polyunsaturated fatty acids are widely used in animal feed, the interests in the fundamental research and applied research of microalgae-based polyunsaturated fatty acids production are increasing. To support the industrial production of algal polyunsaturated fatty acids, studies in recent years have devoted numerous efforts in the algal strains screening, biosynthetic mechanisms exploration, induction conditions optimization, and algae-cultivation mode improvement. Specific factors impacting the biosynthesis of algal polyunsaturated fatty acids include temperature, illumination, salinity, and carbon supply. Two-stage cultivation is proven to be an effective method producing microalgae enriched with polyunsaturated fatty acids. In addition, the use of algal polyunsaturated fatty acids in animal feed has been proven to be a promising way to promote the sustainable development of human society. The addition of algal polyunsaturated fatty acids in feed could not only improve the fatty acid profile of animals, but also enhance the animals' immune responses. Herein, we would likely to summarize the progresses in the aforementioned fields and discuss some critical problems hindering the production and application of algal PUFAs. It is expected that this paper could not only introduce the new knowledge of algal polyunsaturated fatty acids to readers, but also point out the potential development trends of the production and application of algal polyunsaturated fatty acids in the coming future.

Astaxanthin, which is an important metabolite with anti-oxidative property, has been discovered in some fish, shrimp, and microorganisms. Owing to the great advantages of microalgae-based astaxanthin in the aspects of sustainability and safety, microalgal astaxanthin is emerging into the limelight. In the past years, researchers isolated a couple of microalgal species and explored the synthesis pathways of astaxanthin in algal cells. Also, specific culture conditions, such as nitrogen deficiency, high-intensity illumination, and supply of glucose, salt or trace elements, promoting the accumulation of astaxanthin in microalgal cells have been intensively studied. The main goal of this paper is to review the progresses in the production of microalgal astaxanthin and promote the wide use of microagal astaxanthin in aquaculture. In this regard, we summarized the studies on algal strains screening, synthetic mechanisms of microalgal astaxanthin, microalgae cultivation models, and fish-rearing with astaxanthin supplement. Based on the literature review, we discussed the challenges threatening the production and application of microalgal astaxanthin and pointed out the prospects of microalgal astaxanthin in the future. This work will provide a deep understanding of microalgal astaxanthin and its application in aquaculture.

The deposal of residual hydrogen peroxide (H2O2) in Fenton-like system and the requirement of oxygen in bioreactor are essential parts for the treatment of integrative Fenton-like/bioreactor. A novel low-cost integrative Fenton-like and MnO2-filled upward flow biological filter bed (Fenton-like/MBFB) equipped with the modified ceramsite was constructed to evaluate the main properties and catalytic activity of modified ceramsite, and the optimal conditions of integrative system and compare integrative and traditional systems. In this study, the Fenton-like reactor with modified ceramsite had higher catalytic ability whose Acid Orange 7 (AO7) degradation efficiency reached to 79.3% due to large surface area and high porosity, compared with that with raw ceramsite (44.3%). Furthermore, total utilization efficiency of H2O2 in integrative system (from 32.41% to 53.51%) and removal efficiencies of COD and AO7 were remarkably improved, which would effectively decrease the waste of H2O2 and the setting of regulation pool and aeration tank. Thus, the integrative system can save 0.51 CNY/m3 in construction cost and 0.21 CNY/m3 in operating cost. The average COD removal efficiency, AO7 degradation efficiency and effluent DO concentration were achieved to 64.8%, 79.5% and 9.3 mg/L respectively in integrative system were achieved in integrative system during sixty successive runs. Also, the potential degradation pathway of contaminants was also proposed according to the OH-enhanced at Fenton-like reactor due to catalyst and adsorption of modified ceramsite and the removal of microorganisms and modified ceramsite for contaminants at MBFB. This study demonstrated the feasibility of integrative Fenton-like/MBFB filled with modified ceramsite for simultaneously decreasing operational cost and complexity and enhancing removal efficiency, thus provided a one-step alternative for refractory dye wastewater.

Glycerol is important to algal growth, but it is not necessarily right for all wastewater-borne bacteria, especially the beneficial bacterial flora or beneficial bacterium. This study focuses on the microalgal-bacterial community and interactive network analysis between algae and wastewater-borne bacteria to find beneficial bacteria, then identify the effect of glycerol on a beneficial bacterial strain. Microalgal-bacterial remediation shown better nutrients removal and microalgal biomass in centrate wastewater, and glycerol addition considerably increased biomass but inapparently increase nutrients removal. Pseudomonas sp. and Acinetobacter sp. dominated in algal-bacterial system with and without glycerol. Microbial community and environmental factors formed a linkage network in three cultural modes to find the most vital probiotic. The co-cultivation of microalgae and Pseudomonas aeruginosa as a non-fermentative denitrifying phosphate accumulating organism (DPAO) showed co-cultivation dramatically enhanced biomass yield and nutrients removal efficiencies, especially nitrogen and phosphorous. After adding glycerol, in the late stage of co-cultivation, algal-bacterial consortia collapsed, rendering the reduction of treatment efficiency and biomass. Non-fermentative bacteria as main probiotics in algal-based wastewater remediation were required to prepare small-molecule-weight organics as carbon sources. This study expects to optimize design and operation of algal-bacterial wastewater remediation that can be extended to similar carbon-deficit wastewaters simultaneously obtaining higher biomass and removal efficiency.

Eutrophication caused by excessive nitrogen, phosphorous in water body has considerably serious impacts on the production and life of human being. Activated sludge, a biological removal process, is regarded as a promising and sustainable technology for wastewater treatment. In this study, a novel strain of denitrifying phosphate-accumulating organism (DPAO) was isolated from the activated sludge conducted the acclimation of anaerobic/anoxic (A/O) stage and anaerobic/aerobic (A/A) stage. The removal efficiencies of NO3−-N and PO43--P in bioreactor were 98.7 % and 90.7 % respectively. The metabolic activity of DPAOs was improved from 34.43%–98.28% after A/A stage. The genetic identification and morphological and biochemical characteristics of isolated strain were analyzed and discussed to determine it as a non-fermentative Delftia tsuruhatensis. Sodium acetate and ammonium sulfate + peptone were testified to be optimal carbon source and nitrogen for the growth of this strain respectively. Furthermore, the orthogonal test was measured and calculated to find that the order of key factors affecting the growth of this strain was pH > nitrogen > carbon. According to computer response surface methodology, the most suitable medium group for this strain as 4450 mg/L of sodium acetate (carbon source), 1320 mg/L of ammonium sulfate + peptone (nitrogen source) and 7.85 of pH. The findings of this work broadened up our comprehension of the biological removal process for DPAOs during enhanced biological phosphorus removal.

Aiming at simplifying the harvesting procedure, reducing the production cost, and improving the quality of microalgae-based biodiesel, herein, a novel one-step method for oil-rich biomass production and harvesting was proposed by growing Chlorella sp. with Aspergillus sp. in molasses wastewater. Lipid content and fatty acid profile were measured to assess the suitability of microalgal-fungal biomass for biodiesel production. The results showed that the highest biomass yield (4.215 g/L) was obtained when the inoculation ratio of fungi and microalgae was 100. Activities of fungi positive impacted the decolorization of wastewater and the removal of suspended solids. Thus, co-cultivation system had better performance than mono-system of microalgae in the removal of nutrients in wastewater. Analysis of biomass compositions showed that compared with mono-system of microalgae, co-cultivation system produced biomass with higher lipid content (35.2%) and yield microbial cell oil with lower unsaturation degree, potentially increasing the quality of microbial-cell-lipid based biodiesel.