Characteristics and bioactive properties of mannooligosaccharides derived from agro-waste mannans

Mannooligosaccharides (MOS) were derived using Aspergillus oryzae β-mannanase (ManAo) from different mannan-rich agro-wastes, palm kernel cake (PKC), guar gum and copra meal (CM). Guar gum (GG) released higher amount of MOS (56.31% w/w) from which purification of mannobiose (0.68 mg) and mannotriose (1.26 mg) was demonstrated using size-exclusion chromatography. FTIR analysis of mannan hydrolysates showed characteristic peaks in 1200-900 cm^-1 region indicating the presence of MOS. ¹H &¹³C NMR spectra showed presence of anomeric sugar forms of MOS in different mannan hydrolysates. MOS from locust bean gum and guar gum had both α- and β-anomers while PKC and CM had only α-anomer. Growth promotional activities of different MOS were demonstrated using two probiotic Lactobacilli. Besides, enzymatically derived MOS also showed metal (Fe²⁺) chelating and anti-oxidant activities, wherein best anti-glycating agent was evaluated as MOS from PKC. PKC derived MOS showed highest cytotoxicity (74.19%) against human colon adenocarcinoma cell line (Caco-2). This study demonstrated the prebiotic potential of agro-waste derived MOS and possibility of their utilization as a functional food ingredient.