Resourceful treatment of cane sugar industry wastewater by Tribonema minus towards the production of valuable biomass

Advanced treatment and Resource recovery of brewery wastewater by Co-cultivation of filamentous microalga Tribonema aequale and autochthonous Bacteria

To use unicellular microalgae to remove waste nutrients from brewery wastewater while converting them into algal biomass has been explored but high-cost treatment and low-value biomass associated with current technologies have prevented this concept from further attempts. In this study, a filamentous microalga Tribonema aequale was introduced and the alga can grow vigorously in brewery wastewater and algal biomass concentration could be as high as 6.45 g L-1 which can be harvested by a cost-effective filtration method. The alga together with autochthonous bacteria removed majority of waste nutrients from brewery wastewater. Specifically, 85.39% total organic carbon (TOC), 79.53% total dissolved nitrogen (TN), 93.38% ammonia nitrogen (NH3-N) and 71.33% total dissolved phosphorus (TP) in brewery wastewater were rapidly removed by co-cultivation of T. aequale and autochthonous bacteria. Treated wastewater met the national wastewater discharge quality, and resulting algal biomass contained large amounts of high-value products chrysolaminarin, palmitoleic acid (PLA) and eicosapentaenoic acid (EPA). It is anticipated that reduced cost of algal harvesting coupled with value-added biomass could make T. aequale as a promising candidate for brewery wastewater treatment and resource utilization.

Resource recovery and valorization of food wastewater for sustainable development: An overview of current approaches

The food processing industry is one of the world's largest consumers of potable water. Agri-food wastewater systems consume about 70% of the world's fresh water and cause at least 80% of deforestation. Food wastewater is characterized by complex composition, a wide range of pollutants, and fluctuating water quality, which can cause huge environmental pollution problems if discharged directly. In recent years, food wastewater has attracted considerable attention as it is considered to have great prospects for resource recovery and reuse due to its rich residues of nutrients and low levels of harmful substances. This review explored and compared the sources and characteristics of different types of food wastewater and methods of wastewater treatment. Particular attention was paid to the different methods of resource recovery and reuse of food wastewater. The diversity of raw materials in the food industry leads to different compositional characteristics of wastewater, which determine the choice and efficiency of wastewater treatment methods. Physicochemical methods, and biological methods alone or in combination have been used for the efficient treatment of food wastewater. Current approaches for recycling and reuse of food wastewater include culture substrates, agricultural irrigation, and bio-organic fertilizers, recovery of high-value products such as proteins, lipids, biopolymers, and bioenergy to alleviate the energy crisis. Food wastewater is a promising substrate for resource recovery and reuse, and its valorization meets the current international policy requirements regarding food waste and environment protection, follows the development trend of the food industry, and is also conducive to energy conservation, emission reduction, and economic development. However, more innovative biotechnologies are necessary to advance the effectiveness of food wastewater treatment and the extent of resource recovery and valorization.

Enhanced growth and auto-flocculation of Scenedesmus quadricauda in anaerobic digestate using high light intensity and nanosilica: A biomineralization-inspired strategy

Coupling municipal anaerobic digestate (MAD) treatments with microalgal cultivation can concomitantly achieve nutrient removal and microalgal bioenergy production. However, the high cost caused by dilution water and microalgal harvesting is a great challenge. In this study, Scenedesmus quadricauda was screened as the most appropriate algae strain due to its potential for growth and auto-flocculation, and the MAD diluted 5-fold with WWTP effluent was demonstrated as an ideal medium for S. quadricauda growth. Moreover, inspired by naturally generated silica shells of diatoms, a low-cost and biomimetic auto-flocculation strategy that combined high light intensity induction and microalgal silicification was proposed to accelerate the auto-flocculation process. Compared with low light intensity groups, this strategy imparted diatom-like features to S. quadricauda cells, and contributed to 3.07-fold higher auto-flocculation efficiency within 30 min. It was attributed to the fact that the high light intensity of 150 μmol·m ^- 2·s ^- 1 stimulated the extracellular polymeric substances (EPS) secretion and induced the variation in property and composition of EPS, especially the protein secondary structures, which allowed silica nanoparticles to spontaneously attach onto S. quadricauda cells in the presence of viscous EPS. Furthermore, this strategy significantly increased microalgal biomass yield to a dry weight of 1.37 g·L ^- 1, accompanied by 93.78%, 96.39% and 91.36% removals of NH₄⁺-N, TP, and COD, respectively. The productivity of valuable by-products, including lipid, carbohydrate, protein, and pigment, reached 56.30, 101.35, 30.39 and 11.28 mg·L ^- 1·d ^- 1, respectively. Overall, this study supplies a novel approach for low-cost microalgal bioenergy production from MAD and energy-efficient microalgae harvest by auto-flocculation.

The growth, lipid accumulation and adaptation mechanism in response to variation of temperature and nitrogen supply in psychrotrophic filamentous microalga Xanthonema hormidioides (Xanthophyceae)

BACKGROUND

Microalgae are promising feedstocks for production of renewable biofuels and value-added bioproducts. Temperature and nitrogen supply are important environmental and nutritional factors affecting the growth and metabolism of microalgae, respectively. In this study, the growth and lipid accumulation of filamentous microalgae Xanthonema hormidioides under different temperatures (5, 7, 10, 15, 20, 25, 27 and 30 °C) and initial nitrogen concentrations (3, 9, 18 mM) were investigated, and its adaptive mechanisms of tolerance to low temperature and nitrogen stress were analysis by proteomics.

RESULTS

The optimum temperature range for the growth of X. hormidioides was between 15 and 20 °C, and the algal cells had slow growth rate at 5 °C and could not survive at 30 °C. The maximum biomass concentration was 11.73 g L^-1 under the temperature of 20 °C, and the highest total lipid content was 56.63% of dry weight. Low temperature did not change the fatty acids profiles but promoted the accumulation of unsaturated fatty acids of X. hormidioides. The maximum contents of palmitoleic acid, eicosapentaenoic acid and total fatty acid were 23.64%, 2.49% and 41.14% of dry weight, respectively. Proteomics was performed under three temperature (7, 15, 25 °C), two nitrogen concentrations (3 and 18 mM) and two cultivation times (day 3 and 12). A total of 6503 proteins were identified. In the low temperature, photosynthesis-related proteins were down-regulated to protect the photosynthetic apparatus. The up-regulation of key enzymes DGAT and PDAT demonstrated the accumulation of TAGs under low nitrogen treatment. The proteins related to ribosome, phosphatidylinositol signaling system, antioxidant system and cold shock proteins (CSPs) in X. hormidioides were co-upregulated under the treatment of low temperature, which can alleviate the damages induced by temperature stress and maintain the normal growth and metabolism of algal cells.

CONCLUSIONS

X. hormidioides is a psychrotolerant microalga. It is an oleaginous filamentous microalga containing hyper palmitoleic acid and a certain amount of eicosapentaenoic acid with great potential for biofuel development, as well as for applications in nutritional health products and other industries.

Isolation, Characterization and Immunomodulatory Activity Evaluation of Chrysolaminarin from the Filamentous Microalga Tribonema aequale

The aim of this study is to investigate the differences in the accumulation capacity of chrysolaminarin among six Tribonema species and to isolate this polysaccharide for immunomodulatory activity evaluation. The results showed that T. aequale was the most productive strain with the highest content and productivity of chrysolaminarin, which were 17.20% (% of dry weight) and 50.91 mg/L/d, respectively. Chrysolaminarin was then extracted and isolated from this alga, and its monosaccharide composition was mainly composed of a glucose (61.39%), linked by β-D-(1→3) (main chain) and β-D-(1→6) (branch chain) glycosidic bonds, with a molecular weight of less than 6 kDa. In vitro immunomodulatory assays showed that it could activate RAW264.7 cells at a certain concentration (1000 μg/mL), as evidenced by the increased phagocytic activity and upregulated mRNA expression levels of IL-1β, IL6, TNF-α and Nos2. Moreover, Western blot revealed that this polysaccharide stimulated the phosphorylation of p-65, p-38 and JNK in NF-κB and MAPK signaling pathways. Overall, these findings provide a reference for the further development and utilization of algae-based chrysolaminarin, while also offering an in-depth understanding of the immunoregulatory mechanism.

A comprehensive review on emerging trends in industrial wastewater research

Rapid industrialization is one of the intricate factors that is linked to the depletion of water resources and increased generation of wastewater. Due to various obstructions and impediments, such as ineffective treatment solutions, exorbitant prices, lack of basic amenities, insufficient financial assistance, and technical expertise, sustainable treatment of industrial effluents has become an onerous process in most parts of the world. The majority of current treatment solutions are conventional and outdated, and thus fall short to remove all the contaminants efficiently from the industrial wastewater. Moreover, poorly treated or untreated industrial effluents are indiscriminately dumped into water bodies such as lakes, ponds, and rivers, causing substantial health hazards to humans and animals and serious threats to the aquatic ecosystem. Thus, there is a need for highly efficient, cost-effective, and sustainable technologies for the treatment of industrial wastewater. Employment of microbial technologies such as microbial fuel cells and microalgal technologies, treatment of wastewater can be coupled with the production of bioelectricity and valuable biomass, respectively. Moreover, with nanofiltration and biochar technologies, the efficiency of the overall treatment procedure can be increased to a greater extent. The present review aims to highlight opportunities and challenges associated with some of the emerging trends in industrial wastewater research.

Transcriptomic analysis unravels the modulating mechanisms of the biomass and value-added bioproducts accumulation by light spectrum in Eustigmatos cf. Polyphem (Eustigmatophyceae)

Light spectrum can influence microalgal growth and metabolites accumulation significantly. However, the related mechanism has not been fully elucidated. Here, an oleaginous microalga Eustigmatos cf. polyphem, which also featured with high content of palmitoleic acid (POA) and β-carotene, was cultured with LEDs-based red light (RL) and blue light (BL). The results showed that the biomass, total lipid content and POA content were much higher under RL than these under BL, regardless of nitrogen concentration. However, the β-carotene content under RL was significantly lower than that under BL. Transcriptomic analysis revealed that photosynthesis, central carbon metabolism, fatty acid and glycerolipid biosynthesis were elevated, supporting the fast cell growth and high lipid content with POA under RL. In contrast, upregulation of key enzymes in carotenoids biosynthesis and suppression of β-carotene conversion promoted β-carotene accumulation under BL. These findings provide a feasible strategy for promoting lipids, POA and β-carotene in E. cf. polyphem.

Annotated Genome Sequence of the High-Biomass-Producing Yellow-Green Alga Tribonema minus

Here, we report the annotated genome sequence for a heterokont alga from the class Xanthophyceae. This high-biomass-producing strain, Tribonema minus UTEX B 3156, was isolated from a wastewater treatment plant in California. It is stable in outdoor raceway ponds and is a promising industrial feedstock for biofuels and bioproducts.