## 3 Results and Discussion  
### Arthospira Plateensis Fermentation  
One of the aims of the study was the evaluation of solid-state fermentation of _A. platensis_ with _L. casei_ bacteria that could lead not only to the implementation of new lactic acid-fermented food products but also to modifications of algae biomass aromatic fraction. Fermenting a matrix having a high bacterial charge could negatively affect the finished product considering that spoilage and/or pathogenic bacteria may also grow during the process. In this specific case, the biomass utilized for the experiment was cultivated in a raceway pond. This type of cultivation is associated with undesired microflora, such as _Bacillus_ spp., _Aletomonas_ spp., _Flavobacterium_ spp. and _Pseudomonas_ spp. [27], and previous studies have reported a variable concentration of bacteria, ranging from 2 to 7 log CFU/g, in this type of matrix [3]. For this reason, prior to fermentation, carried out for 48 h in sterilized glass cans, samples were subjected to UV radiation treatment (which does not seem to affect _A. platensis_ composition [34]) or sterilization treatment in an autoclave in order to reduce the presence of microbiological contaminants. The UV treatment was ineffective for the reduction of microbial contamination, which was maintained at the same level of untreated samples (5.10 \(\pm\) 0.2 log CFU/g). In order to predict the UV disinfection rates on food surfaces, it is necessary to consider the interactions between microorganisms and surface materials while trying to avoid the shielding effects from incident UV and predict the dependency on the surface structure or topography [35]. For this reason, UV treatment did not reduce the initial microbial contamination because of an uneven distribution of rays in the dehydrated samples. Furthermore, the presence of a high amount of pigments, phenolic compounds and other components with a protective effect against UV rays may contribute to microbial survival [36]. After UV treatment, a fermentation process of 48 h was conducted considering two _Lacticaseibacillus casei_ bacteria. _L. casei_ 2240 and _L. rhamn_ GG concentrations were determined following inoculation, and growth was determined after 24 and 48 h of incubation at 37 \({}^{\circ}\)C. The endogenous contamination did not affect the counts, giving a much more higher LAB inoculation of 7 log CFU/g. As shown in (Figure 1A), the two strains showed a similar growth trend in the UV-treated matrix. After 24 h of fermentation, both species showed good replication capacity, reaching a concentration higher than 9 log CFU/g. In particular, _L. rhamn_ GG increased by 2.23 log CFU/g (from 7.13 \(\pm\) 0.09 to 9.36 \(\pm\) 0.03 log CFU/g; \(p\) < 0.05), and to a higher extent than _L. casei_ 2240 with a growth of 1.78 log CFU/g (from 7.52 \(\pm\) 0.06 to 9.30 \(\pm\) 0.21 log CFU/g). After 48 h of fermentation, a decrease in the concentration of both strains was observed. _L. casei_ 2240 decreased by 0.86 log CFU/g (from 9.30 \(\pm\) 0.21 log CFU/g to 8.44 \(\pm\) 0.28 log CFU/g), while _L. rhamn_ GG decreased by 0.70 log CFU/g (from 9.36 \(\pm\) 0.03 log CFU/g to 8.66 \(\pm\) 0.14 log CFU/g) (Figure 1A) (\(p\) < 0.05). However, the values remained higher than the inoculation. The _L. casei_ 2240 strain has previously been used to ferment other  
Figure 1: Lactic acid bacteria (LAB) growth (log CFU/g) and pH values in _Arthospira platensis_ biomass after 24 and 48 h of fermentation at 37 \({}^{\circ}\)C for _Lacticaseibacillus rhamn_ GG (GG) and _Lacticaseibacillus casei_ 2240 (2240) bacteria: (**a**) UV-treated samples; (**b**) heat-treated samples. Data are represented as average \(\pm\) SD (bars); two replicates for each sample were measured. Letters indicate significant differences (\(p\) < 0.05). matrixes, such as _Himanthalia elongata_, but the growth ability on this brown seaweed was lower than that observed in this study [37]. The best capacity of this strain to grow on _A. platensis_ can be linked to the high amount of proteins and small peptides [2]. _L.