## 4 Discussion  
Over the past decade, the newly observed functions of oligosaccharides have been responsible for their regulatory properties on different organisms [9]; hence the interest in developing efficient processes for the production of oligosaccharides. Therefore, algae polysaccharides were considered as a source of diverse oligosaccharidesacharide structures to the extent that oligosaccharides have demonstrated a role in many important industrial processes, such as brewing [25] and baking [26]. Moreover, it has been largely studied that the degradation products of algae polysaccharides have prebiotic activity [9; 13] and are a potential elicitor of plants' growth and natural defenses [15; 27]. It has therefore become interesting to develop a rapid process which generates with good yield, homogeneous fractions of a low molecular weight. There are many ways to achieve degradation of polysaccharides: enzymatic, physical or chemical [28]. Methods of depolymerization of algae polysaccharides include depolymerization of fucoidan by radical process [29], chemical hydrolysis of carrageenan [30], enzymatic degradation of glucuronan [31], thermal hydrolysis, and enzymatic degradation of alginate [7; 32]. The water soluble alginate from _Bifurcaria bifurcata_ was previously studied [33], and \({}^{1}\)H-NMR analysis of ASBB (Figure 1) reported a higher amount of galvanonic acid, with abundance of homoguluronic blocks (Table 2). Compared to the alignates from other brown algae, the galvanonic acid abundance in ASBB was higher than that observed in alignates of _Cystoseira_ species [34; 35; 36], _F. vesiculosus_[37], _Sargassum_ species [16; 38; 39; 40], _L. japonica_ and _L. digitata_[41; 42]. Similar results are noted in alignates of _C. myrica_ and _L. hyperborea_[23; 35]. However some _Sargassum_ species, notably _S. polycystum_ and _S. filipendula_, were characterized by a higher amount of galvanonic acid [39]. The uronic acids content and the proportions of the homoguluronic blocks determined the physicochemical properties of alginate [43]. Therefore, alginate with a M/G ratio value inferior to 1 form strong and rigid gels [44; 45]. Based on these interpretations and our results (M/G \(<\) 1 and F\({}_{\text{GC}}\) = 0.45), we can confirm that a gel can be formed using ASBB. Despite the gelling property of ASBB, it was recently applicated as an elicitor of natural defense in date palm roots with interesting results [33]. In this context, the development of a rapid and efficient process for a large production of oligo-alignates (ASBB) was the objective of this work, which consisted of the exploitation of alginate of _B. bifurcata_ to produce oligo-alignates (OGABs) with Mw \(\leq\) 5.5 kDa. Several physico-chemical methods of degradation of alginate were already reported, including thermal degradation [32], microwaves [27], Gamma irradiation [46] and ultrasounds [15] for physical processes, as well as enzymatic [7; 46] and radical depolymerizations for (bio)chemical strategies. Among these methods, we adopted a controlled radical hydrolysis using hydrogen peroxide (H\({}_{2}\)O\({}_{2}\)) in small quantities. Hydrogen peroxide has been reported to cause a scission of alginate, xyloglucan, dextran, and pectin [47]. Figure 2 shows that depolymerization in presence of H\({}_{2}\)O\({}_{2}\) was rapid (occurred in 2 h), and after 4 h it remained nearly constant. This was expected since the concentration of H\({}_{2}\)O\({}_{2}\) was exhausted as a function of the reaction time. A similar phenomenon was observed in other reported works [48]. The decrease in molecular weight can be explained by the manifestation of radical attacks at the glycosidic bond, associated with oxidative degradation [49]. When hydrogen peroxide (H\({}_{2}\)O\({}_{2}\)) was added to alginate solution, H\({}_{2}\)O\({}_{2}\) molecules were dissociated to form \(\bullet\)OH active free radicals which are powerful oxidants able to break the glycosidic bonds of alginate.