Cultivation ofDesmodesmus subspicatusin a tubular photobioreactor for bioremediation and microalgae oil production

Abstract

The microalgae Desmodesmus subspicatus (Chlorophyta) was cultivated in a tubular photobioreactor using effluent from the wastewater treatment plant of the University of Santa Cruz do Sul, Brazil to demonstrate the reactor's operation. The algae's ability to remove nutrients from wastewater and the oleaginous potential of the algae's biomass were also evaluated. Total phosphorus and ammonia nitrogen were measured. The photobioreactor consisted of a system of three acrylic tubes, a reservoir, connections and a CO2 supply. The gas supply was semicontinuous with CO2 added from a cylinder. The culture's growth was estimated from cell numbers counted on a daily basis. Lipid content in the biomass was analysed using gas chromatography. A maximum cell density of 9.11 x 10(6) cellsmL-1 and a dry weight of 234.00 mg L-1 were obtained during cultivation without CO2, and these values rose to 42.48 x 10(6) cells mL-1 and 1277.44 mg L-1, respectively, when CO2 was added to the cultivation. Differences in the quality of the effluent and the presence of CO2 did not result in different lipid profiles. The presence ofpalmitic acid and oleic acid was notable. The average extracted oil content was 18% and 12% for cultivation with and without the input of CO2, respectively.

Evaluation of microalgae growth in a mixed‐type photobioreactor system for the phycoremediation of wastewater

“…The genetical patrimony was register as A256CC3. The culture was established from the spontaneous growth of native microalgae, and the amount of inoculum used was determined based on the cell density, starting each experiment with approximately 4,75 × 10 6 mL −1 cells …”

“…The column system was designed to maximize the utilization of incident light, thereby improving the photosynthetic activity of the microalgae. A set of three diaphragm compressors (VigoAr® 300, São Paulo, Brazil) were responsible for used atmospheric air through a diffuser, located in the conical base of the tubes, at a rate of 0.22 vvm −1 from each compressor to promote the homogenization of the cultivation medium as well as gas exchange …”

“…Cell density was determined to measure the growth of the microalgae, and assessed as the daily increase in the number of cells using a cell counter in a Neubauer chamber as the reference method with trinocular microscopy (MLT300, Instrutherm, São Paulo, Brazil). The maximum cell density (MCD) was defined as the maximum cell concentration in cells per milliliter of culture during stationary phase growth, and the cultivation time corresponds to the days elapsed until the MCD was reached . It also monitored the cultivation of microalgae by determining growth rate ( r , d −1 ) expressed as r = (ln( N / N 0 ))/( t – t 0 ), where N is the cell density (in cells mL −1 ), and N 0 is the cell density (in cells mL −1 ) at time t 0 .…”

Biomass from microalgae separation by electroflotation with iron and aluminum spiral electrodes

“…In particular, NaOH is inexpensive and reacts quickly; however, its solutions must be neutralized before disposal. Something that should be considered is the possibility of changing the profile of fatty acids from the biomass depending on the type of flocculating agent used [12][13][14].…”

Microalgae and Clean Technologies: A Review

“…The use of microalgae for bioremediation is a valuable alternative for contaminant removal because in most cases, existing technologies cannot achieve effective treatment of these substances. These microorganisms can assimilate inorganic nitrogen and phosphorus for their own development and can remove potentially toxic metals and organic substances . The combination of microalgae with wastewater can be a suitable alternative for improving clean technologies.…”