## 3 Results and Discussion
### Composition of Microorganisms  
A metagenomic study of the effect of JA addition to maize silage on the bacterial and methanogenic archaeal composition of anaerobic digestate was performed. The analysis was made to assess the effect of bioactive components that are contained in the JA. The structure of the microbial community was analyzed by sequencing the PCR products of the V4 16S rRNA gene amplified by the 515F and 806R primer pairs in five samples. The sequencing run produced 2.13 Gbp of data in total (8,159,519 total reads) with an average error rate of 0.55% and 94.86% of bases passing >Q30 filter. From the five analyzed samples, rarefied to even sequencing depth (63,159 reads), 928 unique ASVs were inferred. Figure 3 shows the composition of the microbial community in different silage samples after 35 days of fermentation. No significant changes were observed in the microbial diversity of the samples. Members of the _Dethiobacteraceae family_, which are very often described as syntrophic acetate-oxidizing bacteria [62], represented between 12-14% of all bacteria in our samples. Members of the _Hungateiclostridiaceae_ family hydrolyves carbohydrates and cellulose to produce CO\({}_{2}\), H\({}_{2}\), acetate, lactate, formate and ethanol [63]. Members of this family represented between 11-13% in our samples. Members of _Clostridiaceae_ family are very important hydrolytic bacteria degrading the lignocellulosic biomass [63]. In our samples, the abundance of _Clostridiaceae_ family ranged from 6% to 8%. Another abundant family was _Lenttimicrobialeae_, with the presence in samples between 7-9%. Members of this family are described as fermentative and hydrolytic organisms able to ferment a wide range of compounds into acetate, malate, propionate, formate, etc. [64]. A large fraction of reads affiliated with uncultured/uncultivated? bacteria of the 8 at order to family level was determined. It represented 9-13% of all bacteria. These microorganisms are correlated with carbohydrate fermentation during anaerobic digestion [62]. Members of the _Synergistaceae_ family ferment organic acids and amino acids (arginine, alanine, glutamic acid, leucine, cysteine), and they also reduce cysteine and elemental sulphur to H\({}_{2}\)S [63]. The members of _Synergistaceae_ family represented 3-4% of all bacteria. Members of the _Thermacetogeniaceae_ family belong to syntrophic acetate-oxidizing bacteria. The _Caldicoprobacteraceae_ family is associated with the direct or indirect involvement in the protein hydrolysis [63] represented 4-6% of all bacteria. Members of the _Dysgonomonadaceae_ family represented 2-3% of all bacteria in the samples. They utilize pyruvate and produce acetic acid and CO\({}_{2}\) as fermentation products [63]. The hypothesis that the addition of JA affected the composition of microorganisms during the fermentation of the samples tested by us cannot be confirmed. In all samples, _Archaea_ represented 0.7-1% of the total. The most abundant _Methanobacteriaceae_ family represented 89-95% of all _Archaea_. Figure 4 shows the major taxonomic subgroups within the phyla. The archaeal community in all samples was dominated by _Euryarchaeota_ (92-96% of total archaea), _Halobacterota_ represented 3-8% of total archaea. Hydrogenotrophic _Methanobacterium_ genus became dominant in all tested samples, reaching relative abun  
Figure 4: Silage samples archaeal 165 rRNA genes relative abundance at the genus level, based on the average ASV reads from triplicates. Sampled on day 35, except the inoculum, which was sampled on day 0. Figure 3: Silage samples bacterial and archaeal 165 rRNA genes relative abundance at family level, based on the average ASV reads from triplicates. Sampled on Day 35, except inoculum, which was sampled on day 0.  
dance levels \(>84\%\) of total archaea on Day 35.