## 3 Results and Discussion
### Arthospira Plateensis Fermentation
The better survivability of _L. casei_ 2240 to lyophilization in sterilized biomass than UV-treated samples was observed on the basis of the applied statistical model (Figure 1). Several authors [17; 48; 49] tested the addition of _A. platensis_ to dairy products, such as yogurt, cheese and fermented milk, with positive results, including an increase in the number of LAB and an improvement in the nutritional quality of the fermented product during storage. The fermentation process leads to increased production of phenolic compounds and phycocyanobilins and consequently increased radical scavenger properties of the cyanobacterium [50]. Lactic acid fermentation is an appropriate method to enhance the functional properties of spirulina and also to integrate beneficial bacteria into consumers' diets, thereby providing further advantages to the final product. However, to meet the definition of probiotic products, microorganisms must be viable for the entire shelf life of the product, and in such quantities to be able to multiply and integrate the intestinal flora. The activity of _A. platensis_ to enhance LAB vitality, such as that of _L. casei, Streptococcus thermophilus, Lacticaseibacillus acidophilus_, and _Bifidobacteria_, has been documented [3; 19; 20; 21]. There is no consensus regarding the minimum quantity of probiotic microorganisms to be ingested to guarantee their functionality in the human intestine. Usually, to observe a positive effect on health, 6 to 7 log CFU/g of live probiotic microorganisms, able to colonize the intestine, should be consumed daily [51]. All of the fermented biomasses obtained in this study presented a sufficient amount of bacteria, allowing the production of fermented foods with a high functional value. An image of the fermented biomasses produced after lyophilization is presented in Figure 2.  
Volatile Profile Characterization of A. platensis and Changes in Volatile Components after Fermentation  
Recently, several studies have been conducted on the characterization of the aromatic fraction of _A. platensis_, and, in particular, a number of studies were carried out with the aim of identifying how the characteristic fishy odor of this product can be reduced in  
Figure 2: Representative image of fermented and lyophilized _Arthospira platensis_ biomasses subjected to UV and sterilization treatments. order to use it as additive or ingredient in food [29; 30; 33]. The reduction of unpleasant aromatic notes can be achieved by solvent extraction [29], such as by fermentation using fungi or bacteria [30; 33]. The deodorization of _A. platensis_ can be performed by applying an extraction procedure to the biomass; [PERSON] et al. stated that the fishy odor can be reduced by treating spirulina with a solvent (e.g., ethanol, acetone or hexane) capable of dissolve aromatic compounds, thereby preserving the nutritional characteristic of the product [29]. On the other hand, fermenting _A. platensis_ with lactic acid bacteria, such as _Lacticaseibacillus plantarum_ or _Bacillus subtilis_, may remove the volatile compounds initially present in the matrix and lead to the formation of new components, such as acetoin, that provide fermented and creamy aromatic notes [30]. In the present study, lactic acid bacteria fermentation was applied to stabilized _A. platensis_ materials, and changes in the volatile fraction were determined. A total of 61 different volatile compounds were identified in the volatile fraction of treated but not fermented and fermented _A. platensis_ samples (Table 1). In particular, 7 aldehydes, 9 ketones, 4 esters, 9 terpen/norisoprenoids, 7 alcohols, 4 furans, 11 hydrocarbons, 7 pyrazines and 3 sulfur compounds were detected. These results are consistent with data reported by [PERSON] et al. (2018), who detected the same classes of volatile compounds in spirulina samples fermented with different strains of _L. plantarum_, _L. acidophilus_ and _Bacillus subtilis_[30]. The class that quantitatively mainly represents the aromatic fraction of _A.