Method for obtaining biomass of red microalga porphyridiumpurpureum

Abstract

FIELD: biotechnology.SUBSTANCE: method for producing biomass of the red microalga Porphyridium purpureum is disclosed. The method involves cultivating Porphyridium purpureum in a sterile Trenkenshu nutrient medium based on seawater in a cumulative mode using a luminostat at 5 klx. Cultivation is carried out in a vortex photobioreactor with stirring using a polycarbonate washer immersed in the suspension at a rotation speed of 30 rpm or a floating washer at a rotation speed of 12 rpm.EFFECT: uniform mixing of the cell suspension and increased productivity of Porphyridium purpureum.1 cl, 2 ex

Description

[0001] Technical field

[0002] The invention relates to the field of biotechnology and can be used in medicine, pharmaceutical, food and cosmetic industries for the industrial production of biomass of the red microalga Porphyridium purpureum, enriched with valuable biologically active compounds (phycoerythrin, exopolysaccharides, polyunsaturated fatty acids).

[0003] Among the many representatives of Rhodophyta, the red unicellular microalgae Porphyridium purpureum is the most popular among industrial-scale producers of biomass and biologically active compounds (Bayu at al., 2023; Fuentes-Grünewald et al., 2015). This species has a number of valuable biotechnological characteristics. 1. The growth of P. purpureum cells is not limited by high concentrations of biogenic elements, including trace elements, which makes it possible to obtain optically dense cultures on highly concentrated nutrient media (Trenkenshu, 1977; Lelekov, 2024). 2. Based on P. purpureum biomass, valuable pigment-protein complexes (R-phycoerythrin), as well as sulfated polysaccharides, including glucuronic acid (Ginzberg et al., 2008) are obtained on an industrial scale. 3. The marine species P. purpureum is characterized by a fairly wide range of changes in salinity in the environment, which allows this species to be grown far from the sea (Kavitha et al., 2016).Therefore, the development of industrial technologies for the intensive cultivation of P. purpureum is an important and urgent task.

[0004] State of the art

[0005] A method for cultivating P. purpureum in parallel-plate photobioreactors is known (RU Patent No. 2823597; RU Patent No. 2675318) with continuous bubbling of the culture with atmospheric air through an aquarium atomizer, which allows for the provision of cell growth with atmospheric carbon. A disadvantage of this method is significant biomass loss due to air bubbles bursting on the surface, leading to cell death (Camacho et al., 2000; Camacho et al., 2001).

[0006] A method for culturing P. purpureum in a 1500-L tubular horizontal photobioreactor (Schoeters et al., 2023), which was housed in an agricultural greenhouse, is known. A pump was used to mix the suspension, circulating the cell suspension through the tubes. A significant drawback of this method is the high hydrodynamic resistance of the cultivation system, as well as the death of the culture due to pressure drops at the impeller edge (Gudin et al., 1991; Sobczuk et al., 2012). Another significant problem with cultivating microalgae in tubular photobioreactors is the fouling of the illuminated surface, which reduces the irradiance of the deeper layers of the suspension.

[0007] A method for culturing P. purpureum in vertically oriented polyethylene sleeves is known (Cohen et al. 1991). The culture was grown in closed polyethylene sleeves (bags) with diameters of 10, 20, and 32 cm. The suspension was stirred by bubbling air enriched with carbon dioxide. A disadvantage of this method is the use of air bubbling, which results in the bubbles bursting on the surface and destroying the cells (Camacho et al., 2000; Camacho et al., 2001). Another significant limitation is the increase in the working volume of the suspension in the sleeves, since an increase in the height of the liquid column leads to high costs for air compression, as well as an increased risk of polyethylene rupture.

[0008] The closest analogue (prototype) of the proposed method is the cultivation of P. purpureum in open pools with mixing by submersible pumps (Borovkov et al., 2025) or by means of a mechanical mixer used in pools (raceway pond) of the circulation type (Skifa et al., 2025).

[0009] This method involves using a rectangular tank in which P. purpureum is cultivated under natural light. A disadvantage of this method is the significant difficulty in mixing large volumes of P. purpureum suspension. This is due to the fact that, as P. purpureum cells grow, they synthesize large quantities of viscous exometabolites, which reduce the flow rate of the culture medium. Increasing the intensity of mixing the viscous medium significantly increases energy costs and also leads to yield loss due to cell death (Sobczuk et al., 2012).

[0010] Disclosure of the essence of the invention

[0011] The objective of the invention is to obtain biomass of the red microalga Porphyridium purpureum on an industrial scale.

[0012] The technical result consists in ensuring uniform mixing of the Porphyridium purpureum cell suspension.

[0013] A vortex-type photobioreactor is used to mix viscous culture media during intensive growth of P. purpureum on an industrial scale. As culture density increases, P. purpureum cells synthesize large amounts of viscous exometabolites, leading to an increase in the viscosity of the culture medium, which reduces the uniformity and efficiency of mixing. A distinctive feature of the hydrodynamic pattern in a vortex-type photobioreactor is that an increase in the viscosity of the medium promotes greater uniformity and efficiency of mixing of the suspension. In other types of photobioreactors, an increase in viscosity leads to the opposite effect—a decrease in the average flow rate, as well as a decrease in efficiency and the formation of stagnant zones.

[0014] Implementation of the invention

[0015] Example No. 1

[0016] The P. purpureum culture obtained from the museum was adapted to intensive cultivation conditions for two weeks. For this, a sterile Trenkenshu nutrient medium based on seawater and an accumulative cultivation mode on a luminostat at 5 klx were used. The adapted culture was used for cultivation in a 15 L vortex photobioreactor with a diameter of 50.5 cm, with a suspension depth of 7.5 cm, with LED lamps that created an irradiance of 300 μmol / (m² * s) on the working surface. Mixing was carried out by rotating a washer made of transparent material immersed in the suspension at a frequency of 30 rpm. As a result, on the linear portion of the accumulation curve, the maximum productivity was PM = 0.22 g / (L * day) or P2 = 16.5 g / (m 2 * day).

[0017] Example #2

[0018] A P. purpureum culture obtained from the museum was adapted to intensive cultivation conditions for two weeks. For this, a sterile Trenkenshu nutrient medium based on seawater and a batch cultivation mode on a luminostat at 5 klx were used. The adapted culture was used for cultivation in a semi-industrial vortex photobioreactor with a volume of 200 L, an area of ​​2.54 m², placed in a greenhouse. Stirring was carried out by rotating a floating polycarbonate washer at a frequency of 12 rpm. On the 10th day of cultivation, the culture reached a maximum density of 1.438 g / L and entered the stationary growth phase. After 10 days of batch cultivation, a maximum productivity of 0.22 g / (L * day) or 17.6 g / (m 2 * day).

Claims

A method for obtaining biomass of the red microalgae Porphyridium purpureum, which involves cultivating Porphyridium purpureum on a sterile Trenkenshu nutrient medium based on seawater in a cumulative mode on a luminostat at 5 klx, characterized in that the cultivation is carried out in a vortex photobioreactor with stirring by a polycarbonate washer immersed in the suspension, with a rotation speed of 30 rpm or a floating washer with a rotation speed of 12 rpm.