Low-temperature-resistant nitzschia aeruginosa and application thereof

Abstract

The invention provides nitzschia glauca capable of resisting low temperature and application of the nitzschia glauca, and the provided nitzschia glauca has the preservation number of CCTCC (China Center For Type Culture Collection) NO: M 20252152. According to the invention, the novel nitzschia oryzae strain with remarkable competitive advantages is successfully screened through a 300MeV proton heavy ion physical mutagenesis technology. The growth rate of the strain in a low-temperature environment of 10-15 DEG C is obviously superior to that of a wild type, and the problem of short outdoor culture cycle in high-latitude areas such as northeast is effectively solved; meanwhile, the mutant strain realizes double increase of biomass and high-value components, the fucoxanthin content of the mutant strain is remarkably increased at normal temperature, the lipid and protein content higher than those of a wild type can still be kept at low temperature, and the mutant strain shows extremely high broad-spectrum temperature adaptability and application economic value.

Description

Technical Field

[0001] This invention belongs to the field of functional microalgae screening and application technology, specifically relating to a low-temperature resistant rhomboid algae and its application. Background Technology

[0002] Rhomboid algae ( Nitzschia palea As a typical freshwater diatom widely distributed globally, *Nyctaginea gracilis* has become a key research focus in the field of microalgae biotechnology due to its extremely high photosynthetic efficiency, rapid growth cycle, and strong adaptability to complex environments. In terms of application value, *Nyctaginea gracilis* cells are rich in unsaturated fatty acids, soluble proteins, and fucoxanthin with significant bioactivity; it shows great industrial potential in the development of functional foods, pharmaceuticals, and aquaculture feed. Especially in aquaculture, its moderate individual size and balanced nutritional composition make it a key natural feed for improving seedling survival rates.

[0003] However, temperature is the core environmental factor limiting the large-scale industrial application of *Nyctaginosa*. In actual outdoor cultivation, this algae exhibits a clear thermophilic characteristic, and its physiological metabolic activities are extremely sensitive to low temperatures. When the water temperature drops below 15°C, the enzyme activity of *Nyctaginosa* significantly decreases, photosynthetic rate is inhibited, leading to slow growth and development or even complete cessation. Figure 2 This sensitivity to low temperatures severely shortens its effective production time in high-latitude regions, limiting outdoor cultivation to the hot summer months, which greatly restricts production efficiency and increases operating costs.

[0004] Especially in Northeast China, the temperature fluctuates drastically and is relatively low during the non-freezing spring and autumn seasons. Existing wild algal strains struggle to maintain normal proliferation rates during this period, which has become a bottleneck restricting the widespread application of *Rhizoctonia solani* in northern regions. Therefore, breeding a superior mutant strain that can maintain efficient reproduction in summer, tolerate temperatures below 15°C, and achieve rapid growth is of significant practical importance for extending the outdoor cultivation period, increasing biomass yield, and promoting the development of regional aquaculture. Summary of the Invention

[0005] The purpose of this invention is to provide a low-temperature resistant rhomboid algae and its applications, thereby overcoming the shortcomings of the prior art.

[0006] This invention first provides a type of algae called Rhomboida scoparia ( Nitzschia palea H*CBac2025001 was deposited on September 29, 2025, at the China Center for Type Culture Collection, Wuhan University, Wuhan, China, with accession number CCTCC NO: M20252152.

[0007] Furthermore, the *Rhizophora glutinosa* provided by this invention is obtained through screening after irradiation mutagenesis.

[0008] As specifically stated in the instruction manual, the irradiation conditions are as follows: algal density is 10. 6 / mL, irradiation rate 10Gy / h, irradiation dose 100Gy, after irradiation, the sample was protected from light for 24h, and then inoculated into solid WC medium and cultured for 7d for screening.

[0009] The present invention also provides another use for the screened chrysophagus rhomboides, which is as a feed for aquaculture.

[0010] In another aspect, the present invention provides an aquaculture feed comprising the aforementioned *Rhizophora branica*.

[0011] This invention successfully screened a new strain of *Nyctaginus* with significant competitive advantages using 300MeV proton and heavy ion physical mutagenesis. This strain exhibits a significantly higher growth rate than the wild type at low temperatures of 10℃-15℃, effectively solving the problem of short outdoor cultivation cycles in high-latitude regions such as Northeast China. Simultaneously, this mutant strain achieves a dual increase in biomass and high-value components. Its fucoxanthin content is significantly increased at room temperature, and it maintains higher lipid and protein content than the wild type even at low temperatures, demonstrating strong broad-spectrum temperature adaptability and significant economic value. Attached Figure Description

[0012] Figure 1 Images of algae Figure 2 This is a growth curve diagram of wild-type *Rhizoctonia solani* at different temperatures. Figure 3 This is a growth curve of three mutant strains at 10℃. Figure 4 This is a growth curve of three mutant strains at 15℃. Figure 5 This is a growth curve of three mutant strains at 30℃. Figure 6 Statistical graph showing the lipid content (A), soluble protein content (B), and fucoxanthin content (C) of wild-type algae strains and 100Gy-7 mutant strains. Detailed Implementation

[0013] This invention utilizes the 300MeV proton and heavy ion accelerator at the Institute of Space Environment and Materials Science, Harbin Institute of Technology, to conduct radiation-induced mutagenesis on *Rhizoctonia solani*. The aim is to break through the cold tolerance limit of existing varieties through advanced physical mutagenesis methods and obtain new low-temperature tolerant strains with significant competitive advantages.

[0014] The present invention will now be described in detail with reference to the embodiments and accompanying drawings.

[0015] The *Rhomboidia glutinosa* strain used in this embodiment was provided by the Key Laboratory of Aquatic Biology, Harbin Normal University. The logarithmic growth phase *Rhomboidia glutinosa* strain was irradiated by the 300 MeV proton and heavy ion accelerator at the Institute of Space Environment and Material Science, Harbin Institute of Technology. One specific irradiation condition was as follows: the algal density was 10... 6 The irradiation rate was 10 Gy / h, and the irradiation doses were 10 Gy, 50 Gy, and 100 Gy. After irradiation, the samples were cultured in the dark for 24 h for pretreatment, and then inoculated into solid WC medium and cultured at a constant temperature for 7 days. Dark brown and darker-colored monoclonal algal strains were selected and cultured separately to obtain candidate monoalgal strains. The candidate monoalgal strains were then screened and cultured at 20 °C according to the three irradiation dose groups. The algal cell density on day 10 was used as the analysis index to establish three mutant libraries containing a total of 46 mutant strains. The mutant libraries were then subjected to multiple rounds of repeated screening, and one mutant strain with a faster growth rate at 20 °C was selected from each irradiation dose group (a total of 3 strains) for subsequent experiments.

[0016] 1. Growth of the three mutant strains at 10℃: The mutant strain was cultured at 25℃ to the logarithmic growth phase, then inoculated into 100 mL of fresh WC (seaweed trace element solution) medium. It was then incubated in a 10℃ light incubator with a light intensity of 4000 lux, a light-dark ratio of 12 h:12 h, and aeration at 200 mL / min. Cell density was monitored periodically, and lost medium was replenished after sampling. Wild-type algae cultured at 25℃ served as a control. The results are as follows: Figure 3 As shown: Although the absorbance values ​​of the three mutant strains were higher than those of the wild type on day 8, only the 100Gy-7 mutant strain grew much faster than the wild type at 10℃.

[0017] 2. Growth of the three mutant strains at 15℃: The mutant strain was cultured at 25℃ to the logarithmic growth phase, then inoculated into 100 mL of fresh WC medium and incubated in a 15℃ light incubator with a light intensity of 4000 lux, a light-dark ratio of 12 h:12 h, and aeration at 200 mL / min. Cell density was monitored periodically, and lost medium was replenished after sampling. Wild-type algae cultured at 25℃ were used as a control. Results are as follows: Figure 4 As shown, only the 100Gy-7 mutant strain showed a significantly higher growth rate than the wild type at 15℃.

[0018] 3. Growth of the three mutant strains at 30℃: The mutant strain was cultured at 25℃ to the logarithmic growth phase, then inoculated into 100 mL of fresh WC medium and incubated in a 30℃ light incubator with a light intensity of 4000 lux, a light-dark ratio of 12 h:12 h, and aeration at 200 mL / min. Cell density was monitored periodically, and lost medium was replenished after sampling. Wild-type algae cultured at 25℃ were used as a control. Results are as follows: Figure 5 As shown, the absorbance values ​​of the 10Gy-13 and 100Gy-7 mutants were greater than those of the wild type on day 8, but the 100Gy-7 mutant had a faster growth rate.

[0019] The selected 100Gy-7 mutant strain was named 100Gy-7 and deposited on September 29, 2025, at the China Center for Type Culture Collection, Wuhan University, China, with accession number CCTCC NO: M 20252152.

[0020] Finally, the 100 Gy-7 mutant strain was selected as a potential algal species for outdoor cultivation in Northeast China. To evaluate the economic value of this algal species, the mutant strain was cultured at 25℃ to the logarithmic growth phase and then inoculated into fresh 1 L WC medium. The cultures were then placed in 15℃ and 25℃ light incubators with a light intensity of 4000 lux, a light-dark ratio of 12 h:12 h, and aeration at 200 mL / min. During the logarithmic growth phase, the fucoxanthin, lipid, and soluble protein contents of the mutant strain were measured. The results are as follows: Figure 6 As shown: at 15℃, there was no significant difference in the components of the mutant strain compared with the wild type; at 25℃, the soluble protein content of the mutant strain was lower than that of the wild type, the lipid content was not significantly different from that of the wild type, while the fucoxanthin content was significantly higher than that of the wild type.

[0021] The above results indicate that the mutant strains screened in this invention can maintain a high growth rate at low temperatures while maintaining the same content of high-value components as the wild type; under normal temperature conditions, some indicators are significantly better than those of the wild type.

Claims

1. A type of rhomboid algae, characterized in that, The preservation number of the *Rhizoctonia solani* is CCTCC NO: M20252152.

2. The *Rhizophora glutinosa* as described in claim 1, characterized in that, The aforementioned *Rhizoctonia solani* was obtained through screening after irradiation mutagenesis.

3. The *Rhizophora glutinosa* as described in claim 1, characterized in that, The irradiation conditions are as follows: algal density is 10. 6 / mL, irradiation rate 10Gy / h, irradiation dose 100Gy, after irradiation, the sample was protected from light for 24h, and then inoculated into solid WC medium and cultured for 7d for screening.

4. The application of the *Rhizophora scoparia* as described in claim 1 as a feed for aquaculture.

5. An aquaculture feed, characterized in that, The aquaculture feed contains the *Rhizophora scoparia* as described in claim 1.

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