## 3 Results and Discussion  
### Dynamics and Specific Rate of C. vulgaris BIN Population Growth  
Figure 1 shows the effects of the peroxide and pyridoxine additives effects on the growth dynamics of _C. vulgaris BIN_ microalgae. The analysis showed that the application of peroxide additives as a stress agent reduced the _C. vulgaris BIN_ biomass growth rate, while the gradual accumulation of oxidation products reduced the population life cycle to 3 days. Thus, H\({}_{2}\)O\({}_{2}\) as an independent stress inducer of carotenogenesis is recommended for addition to the culture medium at the rate of not more than 0.1 mL per 1 dm\({}^{3}\). The combined use of hydrogen peroxide and pyridoxine additives in the cultivation of _C. vulgaris BIN_ microalgae allows us to slightly accelerate the biomass growth. It was revealed that the active growth phase ends after 4-5 days, followed by the stabilization phase.  
[PERSON] et al. [24] proposed, in their study, the use of the byproducts of the wine industry to obtain biomass with a high content of carotenoids. Optimal growth was obtained with the extraction of the wine residues of 5% and 10% wt./rev. With the addition of 10% wine residue, the growth of the biomass in the culture medium stimulates antioxidant activity and the production of carotenoids in _C. sorokiniana_ cells. The wine residue contains tartar and yeast, which are the source of pyridoxine hydrochloride, which cause biomass growth.  
[PERSON], [PERSON], and [PERSON] [25] reported on the effect of the pyridoxine on the intensification of the bio-synthesis of photosynthetic pigments. This is possibly associated with the synthesis of amino acids to be used as precursors for the synthesis of light-trapping pigment-protein complexes. For pigment-protein complexes, chlorophylls are stabilizers and an important cofactor due to their non-covalent interaction with the proteins. This means that, in order to maintain the stability of the newly formed pigment-protein complexes, it is necessary to immobilize a larger number of photosynthetic pigments, primarily chlorophylls, as well as their auxiliary pigment-entrenate-carotenoids.  
It is known that besides stimulating plastic processes, pyridoxine is able to partially neutralize the processes of oxidative stress. [PERSON] [26] showed that pyridoxine significantly increased the activity of protective antioxidant enzymes in _C. vulgaris_, such as peroxidase, superoxide dismutase, catalase and ascorbate peroxidase.  
Figure 2 shows the exponential growth phase of _C. vulgaris BIN_ microalgae in semi-logarithmic coordinates. The approximation of the exponential growth phase is a straight line with the slope tangent corresponding to the value of the population-specific growth rate \(\mu\), in day\({}^{-1}\). The specific growth rate varied from 22 to 25 days\({}^{-1}\). It was noted that the cell fluid of sample 3 had a more saturated dark green color, indicating the increased synthesis of photosynthetic pigments.  
Figure 3 shows the effects of the additives on the pH dynamics in the process of _C. vulgaris_ cultivation. The relationship between the cultivation curves and pH dynamics is noted. According to [PERSON] [26], it is connected to the metabolism of the cells and their photosynthetic activity. The work [27] reports that medium alkalization can occur due to algae absorbing the nitrate form of nitrogen due to the export of ammonium ions' excess during photorespiration and other metabolic processes. The viability indicator of _C. vulgaris_ microalgae is the increase of the medium's acidity agreeing well with the dynamics of the biomass accumulation shown in Figure 1.  
Figure 1: Influence of the additives introduced into the culture medium on the dynamics of the population growth of _C. vulgaris BIN_ microalgae: 1, control (no additives); 2, H\({}_{2}\)O\({}_{2}\) additive; 3, H\({}_{2}\)O\({}_{2}\) additives + pyridoxine.