Isolation of freshwater microalgae and outdoor cultivation using cheese whey as substrate

Enhancement of biomass productivity and biochemical composition of alkaliphilic microalgae by mixotrophic cultivation using cheese whey for biofuel production

The growth of microalgae under alkaline conditions ensures an ample supply of CO2 from the atmosphere, with a low risk of crashing due to contamination and predators. The present study investigated the mixotrophic cultivation of two alkaliphilic microalgae (Tetradesmus obliquus and Cyanothece sp.) using cheese whey as an organic carbon source. The variation in cheese whey concentration (0.5-4.5% (v/v)), culture pH (7-11), and NaNO3 concentrations (0-2 gL-1) was evaluated using central composite design in response to biomass productivity and the contents of lipids, total proteins, and soluble carbohydrates. Both investigated microalgae effectively utilized cheese whey as an organic carbon source. The optimum conditions for simultaneously maximizing biomass and lipid productivity in T. obliquus were 3.5% (v/v) whey, pH 10.0, and 0.5 g L-1 NaNO3. Under these conditions, the biomass, lipid, soluble carbohydrate, and protein productivities were 48.69, 20.64, 7.02, and 10.97 mg L-1 day-1, respectively. Meanwhile, Cyanothece produced 52.78, 11.42, 4.31, and 7.89 mg L-1 day-1 of biomass, lipid, carbohydrate, and protein, respectively, at 4.5% (v/v) whey, pH 9.0, and 1.0 g L-1 NaNO3. The lipids produced under these conditions were rich in saturated fatty acids (FAs) and monounsaturated FAs, with no polyunsaturated FAs in both microalgae. Moreover, several biodiesel characteristics were estimated, and results fell within the ranges specified by international standards. These findings indicate that the mixotrophic cultivation of alkaliphilic microalgae could open new avenues for promoting microalgae productivity through low-cost biofuel production.

Microalgal conversion of whey and lactose containing substrates: current state and challenges

Currently dairy processing by-products, such as whey, still propose a significant threat to the environment if unproperly disposed. Microalgal bioconversion of such lactose containing substrates can be used for production of valuable microalgae-derived bio-products as well as for significant reduction of environmental risks. Moreover, it could significantly reduce microalgae biomass production costs, being a significant obstacle in commercialization of many microalgae species. This review summarizes current knowledge on the use of lactose containing substrates, e.g. whey, for the production of value-added products by microalgae, including information on producer cultures, fermentation methods and cultivation conditions, bioprocess productivity and ability of microalgal cultures to produce β-galactosidases. It can be stated, that despite several limitations lactose-containing substrates can be successfully used for both-the production of microalgal biomass and removal of high amounts of excess nutrients from the cultivation media. Moreover, co-cultivation of microalgae and other microorganisms can further increase the removal of nutrients and the production of biomass. Further investigations on lactose metabolism by microalgae, selection of suitable strains and optimisation of the cultivation process is required in order to enable large-scale microalgae production on these substrates.

Screening of antibiotics to obtain axenic cell cultures of a marine microalga Chrysotila roscoffensis

Due to high growth rate, outstanding abiotic stress tolerance, and rich value-added substances, Chrysotila roscoffensis, belonging to the phylum of Haptophyta, can be considered as a versatile resource for industrial exploitation of bioactive compounds. However, the application potential of C. roscoffensis has drawn attention until just recently, and the understanding related to the biological properties of this species is still scarce. For example, the sensitivities of C. roscoffensis to antibiotics, which is essential for the verification of heterotrophic capacity and the establishment of efficient genetic manipulation system is still unavailable. Aiming to provide fundamental information for future exploitation, the sensitivities of C. roscoffensis to nine types of antibiotics were tested in this study. The results demonstrated that C. roscoffensis exhibited relatively high resistances to ampicillin, kanamycin, streptomycin, gentamicin, and geneticin, while was sensitive to bleomycin, hygromycin B, paromomycin, and chloramphenicol. Using the former five types of antibiotics, a bacteria removal strategy was established tentatively. Finally, the axenicity of treated C. roscoffensis was confirmed based on a multi-strategy method including solid plate, 16S rDNA amplification, and nuclear acid staining. This report can provide valuable information for the development of optimal selection markers, which are meaningful for more extensive transgenic studies in C. roscoffensis. Moreover, our study also paves the way for the establishment of heterotrophic/mixotrophic cultivation modes of C. roscoffensis.

Microalgae Strain Porphyridium purpureum for Nutrient Reduction in Dairy Wastewaters

This paper has approached the study of dairy wastewater treatment and the simultaneous biocompound production by Porphyridium purpureum under continuous light and under a day–night cycle. The main goals were to achieve a reduction in the lactose content of the cheese wastewater that was tested and, at the same time, to obtain added value from the produced compounds, so as to increase the economic value of the process. The results show that biomass production increases proportionally with the concentration of lactose for both of the illumination options. The lactose concentration in the waste stream was reduced over 90% in just 7 days. The exopolysaccharide concentration in the growth medium increased with lactose availability. For the samples that were under constant light stress, the concentration of phycobiliproteins was highest when there was small amounts of lactose in the medium. The content of pigments was higher in the case of the day–night cycle of illumination; these being affected by stress factors such as continuous light and high lactose concentration. The results that were obtained prove that dairy wastewaters that are rich in lactose can be used efficiently for the growth of Porphyridium purpureum, achieving an increase in the biomass concentration and a large reduction of the lactose from this waste stream while obtaining a microalgae biomass that is rich in valuable compounds.

Isolation and Culturing Axenic Microalgae: Mini–Review

Microalgae have several applications in nutraceuticals, pharmaceuticals, cosmetics, biofuel production, and bioremediation, among other fields. Isolation and purification are extremely important for obtaining axenic cultures of microalgae from different environments and crucial for their biotechnological applications, but it is not an easy task. In view of the above, it is fundamental to know the classical and advanced techniques and examples of how scientists from around the globe have applied such methods to isolate several genera and the impact of each step on successful algal purification. This review provides a brief and simple explanation of the methodology for sampling, growth, obtention of unialgal, and posterior axenic culture, which will facilitate the development of novel microalgae-related discoveries and applications for new researchers.