A thermochemical pretreatment process to produce xylooligosaccharides (XOS), arabinooligosaccharides (AOS) and mannooligosaccharides (MOS) from lignocellulosic biomasses

► Effective pretreatment hydrolyzes xylan in biomasses into high yields of XOS. ► This process favored formation of xylooligosaccharides of varying DPs (1-25). ► Evaluation of a pretreatment process is through analysis of reaction products. ► Process evaluation indices include prebiotic yields (%), M-I and O-I and O-M. ► The oligomer-monomer index could be the most reliable pretreatment evaluation index.