1. Introduction
As part of the human diet, FACHB-314 is one of the long-used cyanobacteria, and it is also the first batch of algae bacteria to be industrialized using modern biotechnology (Almomani, 2020; Ambati et al., 2019). FACHB-314 belongs to blue-green prokaryotic microalgae with photosynthesis, filamentous, spiral, and multicellular blue-green microalgae, larger than other types of microalgae (Nematian et al., 2020; Shi et al., 2020). Due to the lack of cellulose in the cell membrane (Ribeiro et al., 2021; Rosenau et al., 2021) is easily digested and absorbed by the human body (Karthikeyan et al., 2020). And it has many benefits to human health, including anti-cancer (Patel et al., 2021), antioxidant (Mustafa et al., 2021), anti-viral (Lupatini Menegotto et al., 2021; Mona et al., 2021) and anti-inflammatory (Basavarajappa et al., 2020; Grossmann et al., 2020; Hazeem et al., 2020). Therefore, it can be used to produce health foods (Keller et al., 2021), cosmetics (Hong et al., 2021b), food additives (Hong et al., 2021a) and medicines (Almomani, 2020). In addition, due to the high content of nutrients in its cells (Guo et al., 2021), it can produce more substances, such as pigments, fatty acids, vitamins, minerals, etc. (Sathasivam et al., 2019; Wang et al., 2019; Yucetepe et al., 2019), especially for the production of phycocyanin (Akter et al., 2021), which content can reach 10-20% (Rosa et al., 2019).
Phycocyanin is composed of apolipoprotein (Fu et al., 2021) and phycocyanin (Liu et al., 2019). Apolipoprotein binds to phycocyanin through ether-sulfur bonds (Li et al., 2019). The protein part is composed of the α subunit and β subunit (Karakas et al., 2019; Kashyap et al., 2019). Due to the presence of open-chain tetrapyrrole, it is an auxiliary photosynthetic pigment, and its color is dark blue (Alagawany et al., 2021; He et al., 2019). It is a non-toxic pigment protein with good water solubility (Ferreira-Santos et al., 2021), antioxidant, anti-inflammatory, neuroprotective, and liver protective effects (Ambati et al., 2019; Buchmann et al., 2019; Dalu et al., 2019). It’s the research object of many scholars. In the food industry, phycocyanin is mainly used as a natural dye to replace artificial dyes that are harmful to human health (Ye et al., 2018; Zhang et al., 2018). In the medical field, the absorption and emission wavelengths are high, the fluorescence quantum yield and light stability are good, the extinction coefficient is large, and the solubility in water is high (Thirumdas et al., 2018; Wang & Lan, 2018). Therefore, based on the properties of phycocyanin, can also be used as a fluorescent label (Sengupta et al., 2018).
However, as a phycocyanin extracted from biological algae, its application has certain limitations, such as low yield and difficulty in large-scale production (Rizwan et al., 2018; Rodrigues et al., 2018). Therefore, the main method to overcome such limitations is to increase biomass (because of its higher value) and increase the content of valuable products produced by cell metabolism (Ozkaleli & Erdem, 2018; Raji et al., 2018). In recent years, the importance of nanomaterials has greatly increased (Wang et al., 2017). Based on previous studies, titanium dioxide (TiO2) nanoparticles (NPs) are currently one of the most widely used nanomaterials (Nguyen et al., 2018; Ozkaleli & Erdem, 2018). However, in such studies, we found that TiO2 has a certain inhibitory and toxic effect on the growth of algae cells due to its relatively poor biocompatibility and strong cytotoxicity (Zhou et al., 2021; Zhu et al., 2021). For this, we creatively upgrade materials, Synthesized rGO-TiO2composite nanomaterials for the co-cultivation of Spirulina.
This work fabricated highly biocompatible rGO-TiO2nanoparticles to be used in the cultivation process of FACHB-314 . Aims to improve the absorption and utilization of light by algae, and promote the growth of algae cells and the accumulation of photosynthesis, thereby increasing the production of phycocyanin. In the process of microalgae cultivation, increasing the production of own cells can also increase the output of phycocyanin. Developing a technology that can effectively synthesize phycocyanin inFACHB-314 and explore the feasibility of the corresponding technology.