Bio-process development for sustainable, large-scale production of LAB-oligosaccharides as a potential anti-colon-cancer metabolites produced by Lactobacillus acidophilus 20079.

Abstract

Lactic acid bacteria and their metabolites have shown promising biological activities against different types of cancer, esspecially, colon cancer. In our previouse study, we extracted and optimized the production of a mixture of three oligosaccharides from Lactobacillus acidophilus DSMZ 20079 at the laboratory scale using statistical experimental designs and the active oligosaccharide HPLC fraction was identified as LA-EPS-20079. Also, the anticancer activity of the extracted LA-EPS-20079 against colon cancer CaCo-2 cell line was confirmed via the downregulation of the gene expression of Bcl2 and Survivin genes (6). In the present study, we produced a mixture of bioactive oligosaccharides from L. acidophilus DSMZ 20079 in 10 L bioreactor that maintained the anti-colon cancer against CaCo-2 cell line effects, which is a major transition towards the semi industrial level. To that end, a batch fermentation was carried out in a 10 L bioreactor under uncontrolled pH condition, starting at pH 6.0. During the fermentation process, the bacterial cell mass was increased exponentially with a constant specific growth rate (µ) of 0.07 h^-1, reaching a maximum biomass of 6.93 g L^-1 at 44 h. Also, the concentration of the produced total exooligosaccharides gradually increased and reached a maximum concentration of 1461.43 µg mL^-1 at 40 h post-incubation. Furthermore, the glucose consumption rate was 1.21 g L^-1 h^-1, while the LAB-oligosaccharide production rate reached 96.22 µg mL^-1 h^-1. Moreover, oligosaccharides chemical composition was studied after scaling up the production process using 1D and 2D proton and carbon NMR, along with monomeric composition analysis. The results indicated that LAB-oligosaccharide is a mixture of oligosaccharides, not a single structure, and the mixture consists of three monomeric sugars; herein, we referred to the oligosaccharide mixture as LAB-oligosaccharide. Additionally, the anticancer activity of LAB- oligosaccharide was tested in samples collected from the bioreactor at 0, 12, 14, 16, 18, 20, 22, 24, 36, 40 and 44 h time points against the CaCo-2 cancer cell line. The results confirmed the in-vitro anticancer activity with maximum inhibition percentages of 72.01% and 81.7% after 22 and 24 h, respectively. On the other hand, to establish an environmentally friendly production process, we evaluated the efficacy of using the bacterial biomass residue after LAB- oligosaccharide extraction as a substrate for bacterial isolates growth to produce industrially important enzymes (Lipases and proteases). In this context, 5 bacterial isolates were found to produce both enzymes. These bacterial isolates were characterized using 16S-rRNA gene sequencing and the relatedness between the isolates was studied using phylogenetic analysis. The results demonstrated that the residual biomass supported the growth of B. subtillis PX205316 (2F) for the production of commercially valuable lipase and protease enzymes, hence, the recommended bioprocess was efficient in producing substrate with potential anticancer properties in a process that is environmentally friendly that promotes environmental sustainability.