Stochastic LCA Model of Upscaling the Production of Microalgal Compounds

Microalgae are currently being investigated for their promising metabolites but assessing the environmental impact of producing these compounds remains a challenge. Microalgae cultivation performance results from the complex interaction of biological, technological, geographical, and physical factors, which bioengineers try to optimize during the upscaling process. The path from the discovery of a microalgal compound to its industrial production is therefore highly uncertain. Nonetheless, it is key to anticipate the potential environmental impacts associated with the future production of a microalgal target compound. This is achieved in this study by developing an ex-ante, parameterized, and consequential LCA model that performs dynamic simulations of microalgae cultivation. The model is applied to calculate the environmental impacts of 9000 stochastically generated combinations of photobioreactor geometries and operational setups. The demonstration of the model is done for a fictive microalgal strain, parameterized to resemble Chlorella vulgaris, and a fictive target compound assumed to be a carbohydrate. The simulations are performed in Aalborg, Denmark, and Granada, Spain to appreciate geographical variability, which highly affects the requirements for thermoregulation. Open-source documentation allows full reproducibility and further use of the model for the ex-ante assessment of microalgal products.

Optimization of Astaxanthin Recovery in the Downstream Process of Haematococcus pluvialis

Astaxanthin derived from Haematococcus pluvialis is a valuable metabolite applied in a wide range of products. Its extraction depends on a sophisticated series of downstream process steps, including harvesting, disruption, drying, and extraction, of which some are dependent on each other. To determine the processes that yield maximum astaxanthin recovery, bead milling, high-pressure homogenization, and no disruption of H. pluvialis biomass were coupled with spray-drying, vacuum-drying, and freeze-drying in all possible combinations. Eventually, astaxanthin was extracted using supercritical CO2. Optimal conditions for spray-drying were evaluated through the design of experiments and standard least squares regression (feed rate: 5.8 mL/min, spray gas flow: 400 NL/h, inlet temperature: 180 °C). Maximal astaxanthin recoveries were yielded using high-pressure homogenization and lyophilization (85.4%). All combinations of milling or high-pressure homogenization and lyophilization or spray-drying resulted in similar recoveries. Bead milling and spray-drying repeated with a larger spray-dryer resulted in similar astaxanthin recoveries compared with the laboratory scale. Smaller astaxanthin recoveries after the extraction of vacuum-dried biomass were mainly attributed to textural changes. Evaluation of these results in an economic context led to a recommendation for bead milling and spray-drying prior to supercritical CO2 extraction to achieve the maximum astaxanthin recoveries.

Nutrient recycling from the effluent of a decentralized anaerobic membrane bioreactor (AnMBR) treating fresh domestic wastewater by cultivation of the microalgae Acutodesmus obliquus

This study investigates the feasibility of microalgae cultivation with the effluent (permeate) of a decentralized anaerobic membrane bioreactor (AnMBR) treating high strength domestic wastewater. Two experiments, consisting of three and two successive batch experiments with incubation times varying between 5 and 9 days, were conducted. Nutrient removal and growth of the microalgae species Acutodesmus obliquus were studied for the following culture media: (A) permeate, (B) permeate enriched with iron (Fe), magnesium (Mg), manganese (Mn), sulfur (S) and the chelating agent EDTA, (C) commercial fertilizer as control culture. Initial nutrient concentrations in the culture media ranged from 9.3 to 16.6 mg·L^-1 total phosphorus (TP) and from 85.1 to 126.2 mg·L^-1 total nitrogen (TN). TP reached an average removal of 97%, 98% and 99% in (A), (B) and (C) respectively. An average TN removal of 94% and 96% was achieved in (B) and (C). Starting from the third batch of the first experiment and the second batch of the second experiment, the culture with permeate (A) showed a decrease in TN removal. Further batch experiments showed the need to add iron to ensure an optimal TN removal from the permeate.

Responses of photosystems I and II of Acutodesmus obliquus to chemical stress caused by the use of recycled nutrients

Nutrients derived from hydrothermal gasification of Acutodesmus obliquus were tested on its biological compatibility to support growth of the same microalgae. Photosynthetic parameters of photosystems I and II (PS I and PS II) were investigated to study physiological effects on the microalgal cell. The nutrients were collected as liquid residues. Dilutions of 1:500 showed no effect on both photosystems. Lower dilutions affected PS II initially and later also PS I. Cyclic electron flow around PS I compensated for loss of electrons due to partially inhibited PS II. The highest tested concentration of liquid residue erased any photosynthetic activity of PS II after 28 min and onwards. In contrast, PS I remained active. The results suggest that PS I is less susceptible than PS II and that the mixture of chemicals in the liquid residue did not directly affect PS I but PS II. The toxicants in the residues seemed to interfere with linear electron flow of PS II even though light-driven formation of radicals and subsequent damage to one of the photosystems can be excluded as demonstrated in darkness. Lowered photosynthetic activity of PS I during actinic irradiation was caused due to lack of supply of electrons from PS II. The cyclic electron flow might play a key role in delivering the energy needed to restore PS II activity and to biodegrade the toxicants when linear electron flow failed. These negative effects of liquid residue towards microalgal cells require a remediation step for direct application of the liquid residue to substitute commercial fertilizers in microalgal mass cultures.

[Metastatic Crohn's disease: manifestation in head and neck region]

In addition to mucosal manifestation in the gastrointestinal tract metastatic Crohn's disease also involves cutaneous sites. We report on a 33 year-old female suffering from diarrhea, aphthous ulceration and recurrent granulomatous abscesses on different cutaneous sites also involving the head neck region. Besides a general infection constellation, histologic examination of affected skin and mucosa revealed ulceration with chronic-granulomatous inflammation with Langerhans giant cells. Taking together the intestinal and cutaneous lesions and their histologic appearance as well as the clinical features lead to metastatic Crohn's disease. The patient recovered under immunosuppressive drugs. Metastastic Crohn's disease is a rare and severe form of the well known autoimmune disease which needs interdisciplinary diagnostic and therapy.

[Angiosarcoma of the temporal bone]

Angiosarcoma of the temporal bone is an extremely rare malignant tumor, which originates from vascular endothelium. We describe a case of a 57-year-old woman, initially presenting with progressive hearing loss, otorrhea as well as facial palsy diagnosed as a mastoiditis elsewhere. After subtotal mastoidectomy histological examination revealed an angiosarcoma of the mastoid. Since the tumor was not completely removed lateral petrosectomy and postoperative radiotherapy were performed. Afterwards the patient developed local recurrence with intracerebral tumor extension. During palliative polychemotherapy the patient developed a pneumonia and deceased. In this manuscript the morphology, imaging characteristics and current treatment options of angiosarcomas of the lateral skull base are reviewed and discussed.