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The production of reactive oxygen species (ROS) is an unavoidable consequence of oxygenic photosynthesis and represents a major cause of oxidative stress in phototrophs, having detrimental effects on the photosynthetic apparatus, limiting cell growth, and productivity. Several methods have been developed for the quantification of cellular ROS, however, most are invasive, requiring the destruction of the sample. Here, we present a new methodology that allows the concurrent quantification of ROS and photosynthetic activity, using the fluorochrome dichlorofluorescein (DCF) and in vivo chlorophyll a fluorescence, respectively. Both types of fluorescence were measured using an imaging Pulse Amplitude Modulation (PAM) fluorometer, modified by adding a UVA-excitation light source (385 nm) and a green bandpass emission filter (530 nm) to enable the sequential capture of red chlorophyll fluorescence and green DCF fluorescence in the same sample. The method was established on Phaeodactylum tricornutum Bohlin, an important marine model diatom species, by determining protocol conditions that permitted the detection of ROS without impacting photosynthetic activity. The utility of the method was validated by quantifying the effects of two herbicides (DCMU and methyl viologen) on the photosynthetic activity and ROS production in P. tricornutum and of light acclimation state in Navicula cf. recens Lange-Bertalot, a common benthic diatom. The developed method is rapid and non-destructive, allowing for the high-throughput screening of multiple samples over time., (© 2022. The Author(s), under exclusive licence to Springer Nature B.V.)

Time-resolved monitoring of microalgae agglomeration facilitates screening of coagulants/flocculants (CFs) from numerous biopolymer candidates. Herein, a filtering-flowing analysis (FFA) apparatus was developed in which dispersed microalgal cells were separated from coagulates and flocs formed by CFs and pumped into spectrophotometer for real-time quantification. Polysaccharides-based CFs for Microcystis aeruginosa and several other microalgae were tested. Cationic hydroxyethyl cellulose (CHEC), chitosan quaternary ammonium (CQA) and cationic guar gum (CGG) all triggered coagulation obeying a pseudo-second-order model. Maximal coagulation efficiencies were achieved at their respective critical dosages, i.e., 0.086 g/g M.a. CHEC, 0.022 g/g M.a. CQA, and 0.216 g/g M.a. CGG. Although not active independently, bacterial exopolysaccharides (BEPS) aided coagulation of M. aeruginosa and allowed near 100% flocculation efficiency when 0.115 g/g M.a. CQA and 1.44 g/g M.a. xanthan were applied simultaneously. The apparatus is applicable to other microalgae species including Spirulina platensis , S. maxima , Chlorella vulgaris and Isochrysis galbana . Bio-based CFs sorted out using this apparatus could help develop cleaner processes for both remediation of harmful cyanobacterial blooms and microalgae-based biorefineries.

Development of renewable and clean energy as well as bio-based fine chemicals technologies are the keys to overcome the problems such as fossil depletion, global warming, and environment pollution. To date, cultivation of microalgae using wastewater is regarded as a promising approach for simultaneous nutrients bioremediation and biofuels production due to their high photosynthesis efficiency and environmental benefits. However, the efficiency of nutrients removal and biomass production strongly depends on wastewater properties and microalgae species. Moreover, the high production cost is still the largest limitation to the commercialization of microalgae biofuels. In this review paper, the state-of-the-art algae species employed in livestock farm wastes have been summarized. Further, microalgae cultivation systems and impact factors in livestock wastewater to microalgae growth have been thoroughly discussed. In addition, technologies reported for microalgal biomass harvesting and CO 2 mass transfer enhancement in the coupling process were presented and discussed. Finally, this article discusses the potential benefits and challenges of coupling nutrient bioremediation, CO 2 capture, and microalgal production. Possible engineering measures for cost-effective nutrients removal, carbon fixation, microalgal biofuels and bioproducts production are also proposed., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A cost-effective and environmentally friendly method for biofuel production was developed, by utilizing duckweed as feedstock for biohydrogen production through dark fermentation and simultaneously using the fermentative waste to produce microalgal lipids. The results suggested that acid hydrolysis (1% H 2 SO 4 ) was more suitable for the pretreatment of duckweed biomass. Maximum hydrogen production of 169.30 mL g -1 dry weight was determined under a temperature of 35 °C and an initial pH of 7.0. After the dark fermentation, the volatile fatty acids (VFAs) including acetate and butyrate, were detected in the waste, with concentration determined as 1.04 g L -1 and 1.52 g L -1 , respectively. During the mixotrophic cultivation of Chlorella sacchrarophila FACHB-4 using waste as feedstock, the maximum microalgal biomass and the lipid productions were about 2.8 and 33 times higher with respect to the autotrophic growth. The simultaneous biohydrogen production and waste utilization method provided a green strategy for biofuel production., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

This paper investigates the flocculation of Chlorella sorokiniana suspensions with a novel cellulose derivative, namely hairy cationic nanocrystalline cellulose (CNCC). CNCC are a brand new family of nanocellulose characterized by having two positively charged amorphous ends joint through a common crystalline shaft. Flocculation was monitored through laser reflectance and its mechanism was studied by means of zeta potential, fractal dimension and turbidity removal. CNCC dosage and shear rate were varied and their effect on floc morphology and filterability were assessed. CNCC effectively flocculated the cultures at dosages well below and over the isoelectric point, being the flocculation mechanisms and floc strength highly dependent on the doses applied. The filtration propensity of flocculated suspensions proved highly sensitive to small differences in flocs' geometry. The aggregation process entailed two phases, a first one in which the CNCC adsorbed on the surface of microalgal cells according to a flat random deposition up to reaching a maximal cell coverage, and a second one in which the free spots left were progressively covered with orthogonally deposited CNCC, being this later configuration the main responsible for intercellular attachment. The present work demonstrates that CNCC is an effective flocculant of microalgal cell suspensions and constitutes an alternative worth exploring for the aggregation of other cells' suspensions., (Copyright © 2019 Elsevier B.V. All rights reserved.)