Microalgal photosynthetic inhibition and mixotrophic growth in Post Hydrothermal Liquefaction Wastewater (PHW)

Aqueous phase recycling: impact on microalgal lipid accumulation and biomass quality

The potential success of microalgal biofuels greatly depends on the sustainability of the chosen pathway to produce them. Hydrothermal liquefaction (HTL) is a promising route to convert wet algal biomass into biocrude. Recycling the resulting HTL aqueous phase (AP) aims not only to recover nutrients from this effluent but also to use it as a substrate to close the photosynthetic loop and produce algal biomass again and process this biomass again into new biocrude. With that purpose, the response to AP recycling of five Chlorellaceae strains was monitored over five cultivation cycles. After four successive cycles of dynamic growth under nutrient-replete conditions, the microalgae were cultivated for a prolonged fifth cycle of 18 days in order to assess the impact of the AP on lipid and biomass accumulation under nutrient-limited conditions. Using AP as a substrate reduced the demand for external sources of N, S, and P while producing a significant amount of biomass (2.95-4.27 g/L) among the strains, with a lipid content ranging from 16 to 36%. However, the presence of the AP resulted in biomass with suboptimal properties, as it slowed down the accumulation of lipids and thus reduced the overall energy content of the biomass in all strains. Although Chlorella vulgaris NIES 227 did not have the best growth on AP, it did maintain the best lipid productivity of all the tested strains. Understanding the impact of AP on microalgal cultivation is essential for further optimizing biofuel production via the HTL process.

How Synthesis of Algal Nanoparticles Affects Cancer Therapy? - A Complete Review of the Literature

The necessity to engineer sustainable nanomaterials for the environment and human health has recently increased. Due to their abundance, fast growth, easy cultivation, biocompatibility and richness of secondary metabolites, algae are valuable biological source for the green synthesis of nanoparticles (NPs). The aim of this review is to demonstrate the feasibility of using algal-based NPs for cancer treatment. Blue-green, brown, red and green micro- and macro-algae are the most commonly participating algae in the green synthesis of NPs. In this process, many algal bioactive compounds, such as proteins, carbohydrates, lipids, alkaloids, flavonoids and phenols, can catalyze the reduction of metal ions to NPs. In addition, many driving factors, including pH, temperature, duration, static conditions and substrate concentration, are involved to facilitate the green synthesis of algal-based NPs. Here, the biosynthesis, mechanisms and applications of algal-synthesized NPs in cancer therapy have been critically discussed. We also reviewed the effective role of algal synthesized NPs as anticancer treatment against human breast, colon and lung cancers and carcinoma.

Off-line two-dimensional separation involving supercritical fluid chromatography for the characterization of the wastewater from algae hydrothermal liquefaction

An off-line multidimensional method involving liquid chromatography combined with supercritical fluid chromatography was developed for the characterization of the wastewater of hydrothermal liquefaction of microalgae Chlorella sorokiniana. The first dimension consisted of a phenyl hexyl column operated in reversed-phase mode, whereas the second dimension was performed on a diol stationary phase. Optimization of the kinetic parameters of the first and second dimensions were performed, taking into account the fraction collection system. The beneficial effect of working at high flow rate in both dimensions, as well as the need to work with short columns (50 mm) in the second dimension was evidenced. Injection volume was also optimized in both dimensions. The first dimension benefited from on-column focusing, while in the second dimension, untreated water-rich fractions could be injected without peak deformation. The performances of offline LCxSFC were compared to LC-HRMS, SFC-HRMS and LCxLC-HRMS for the analysis of the wastewater. Despite a long analysis time of 3.3h, the off-line separation coupled to high-resolution mass spectrometry exhibited a very large orthogonality with 75 % occupation rate of the separation space, reaching an effective peak capacity of 1050. While other evaluated techniques were faster, one-dimensional techniques failed to separate the numerous isomers while LCxLC exhibited lower orthogonality (45% occupation rate).

Microalgae adaptation as a strategy to recycle the aqueous phase from hydrothermal liquefaction

Hydrothermal liquefaction (HTL) produces bio-crude oil from wet algae along with an aqueous phase (AP). This effluent contains minerals that can be reused for cultivating new microalgae but whose utility remains limited due to the presence of inhibitors. Reduced photosynthetic performance, growth, and null lipid accumulation were observed in wild-type Chlorella vulgaris NIES 227 cultivated in AP (1/200). Adaptive laboratory evolution was studied by batch transfers and turbidostat mode. Both methods effectively counterbalanced AP toxicity and restored the fitness of the microalgae. After adaptation, a higher AP addition was achieved, from 1/600 to 1/200, without inhibition. As compared with the wild typein control medium (0.261 g/L/d), both adapted-strains maintained competitive productivity (0.310 and 0.258 g/L/d) of lipid-rich biomass (37 %-56 %). The improved tolerance of the adapted strains persisted after the removal of AP and under axenic conditions. Adaptive laboratory evolution is suggested for AP reutilization in the algae production process.

Effects of process water obtained from hydrothermal carbonization of poultry litter on soil microbial community, nitrogen transformation, and plant nitrogen uptake

Process water (PW) obtained from hydrothermal carbonization of nitrogen-rich (N-rich) biowaste is proposed to be a renewable resource utilized as a liquid N fertilizer. However, its effects on soil microbial community, N transformation, and plant N uptake are unclear or controversial. In this study, fertilizers were prepared with different percentages of PW (poultry litter, 220 °C 1 or 8 h, PW-S or -L) and urea to supply 160 mg kg^-1 total N in a barren alkali soil. Results showed that the addition of PW relative to pure urea decreased organic N mineralization by low bio-accessibility, increased N loss by high soil pH, and decreased NO₃^--N by low nitrification substrate. It supported the lettuce in health but decreased plant N uptake by low NO₃^--N. It significantly increased the gram-positive bacteria that responded to resistant organic matter, changed the bacterial community to enhance decomposition, detoxification, ureolysis, and denitrification, and to decrease nitrification. Its inhibition effect on nitrification activity was stronger than that on nitrifiers growth. Different from PW-S, the addition of PW-L seriously and significantly decreased seed germination index and fungal biomass that responded to N retaining capacity, respectively. The best fertilizer was 50% urea +50% PW-S that supported the seed germination and seedling growth, and mildly affected microbial community.