Conversion of sacha inchi ( Plukenetia volubilis L.) residues into potential prebiotic oligosaccharides

Optimal conditions for the production of oligosaccharides from sacha inchi shell (SL) and defatted kernel cake (KC) were studied by combining chemical and enzymatic treatments. Growth enhancement of Lactobacillus spp. and resistance to digestion under simulated gastrointestinal conditions were also assessed. SL and KC powders were subjected to alkali, delignification, and combined alkali and delignification pretreatments. The pretreated materials were then hydrolyzed by the commercial cellulases cellulase SS (CSS) and cellulase XL-531 (CXL). Pretreating SL with delignification and pretreating KC with alkali before hydrolysis by CSS gave the highest content of reducing sugars and various types of oligosaccharides. Response surface methodology gave optimized conditions for SL oligosaccharide (SLO) as 60 °C, 4 h, and pH 5.14 with an enzyme concentration of 1.52% (v/v), while optimized KC oligosaccharide (KCO) was recorded at 45.68 °C, 4.5 h, and pH 4 with an enzyme concentration of 1.05% (v/v). The crude oligosaccharides were then purified by Saccharomyces cerevisiae , which removed 80.80% and 99.97% of glucose from SLO and KCO, respectively. Both SLO and KCO profiles were analyzed by thin layer chromatography (TLC), containing cellobiose, xylobiose, and xylotriose. The oligosaccharides were evaluated for their prebiotic properties—enhancement of the growth of Lactobacillus brevis , L. delbrueckii subsp. bulgaricus , and L. plantarum . SLO stimulated probiotic growth more than KCO. The oligosaccharides also promoted growth of L. brevis , with a highest specific growth rate similar to that of commercial xylo-oligosaccharides. SLO withstood in vitro digestion (77.89% being retained), demonstrating the prebiotic potential of SL for oligosaccharide production.