## 1 Introduction  
As a major source of protein, soybean has been one of the most important crops in China since more than five thousand years and nowadays often appears in Western diets [1]. Soybean has high nutritional value and is recognized as a functional food that both promotes health and has therapeutic effects [2]. For example, soybean contains a high concentration of isoflavues, which are indicated to have benefits in reducing risk of multiple diseases, such as hormone-dependent cancers, and age-related cognitive decline [3]. Soybean is also believed to have antioxidant activity, due to its high amount of total phenolics, that may help neutralize harmful free radicals and reduce the risk of degenerative diseases [4]. Germination technology, which is an inexpensive and effective method, was applied to improve the taste and enhance the nutritional value of soybean [5]. During germination, the endogenous enzymes in soybean are activated and storage nutritional compounds are converted to bioactive components. As a result, the nutrient levels, bioavailability, and palatability are improved [6]. For example, vitamin C, which is famous for its physiological functions in animals and plants, barely exists in soybeans and significantly increases in soybean sprouts. Most importantly, germination is conducive to the accumulation of phenolics and flavonoids, which have antioxidant activity [7]. Furthermore, the sprouts of soybeans have been shown to be effective as an anti-hypertensive diet [8]. At the same time, germination can reduce or remove anti-nutritional factors in soybean, such as a-galactoside,trypsin inhibitor, phytic acid, lectin, and lipase inhibitor [9]. Germination technology expands the application of soybean in food processing and improves its utilization value. Most of the functional ingredients in plants are secondary metabolites, which are biosynthesized as a defense response to different stresses. Hence, the accumulation of secondary metabolites may be stimulated by various elicitors [10]. Chitosan (poly [\(\beta\)-(1-4)-2-amino-2-deoxy-d-glucopyranose]) is an environmentally-friendly and biocompatible cationic polysaccharide, which is obtained by partially deacetylated chitin extracted from naturally occurring crustacean shells [11]. Studies have shown that chitosan can elicit defense responses with respect to callose formation, phytoalexin induction, and lignification [12]. Chitosan can also be employed in the treatment of soybean to enhance the yield and quality of soybean sprouts [13,14]. According to [PERSON] et al., chitosan effectively increased the growth of soybean sprouts without adverse effects on the nutritional and postharvest characteristics [15]. Recently, [PERSON] et al. reported that chitosan pre-soaking could improve the growth and quality of yellow soybean sprouts during germination, dependent on concentration [16]. However, application of chitosan is limited due to its poor solubility under physiological conditions. Recent studies showed that the hydrolytic product of chitosan, a water-soluble chitol oligosaccharidesacharide, also has elicitor activity in seed germination [17]. Furthermore, chitol oligosaccharidesacharide has a great advantage when utilized as antimicrobial agents, antioxidants, and enhancers of the nutritional quality of food, while molecular weight is identified as a main characteristic of chitol oligosaccharidesacharide that is closely associated with the biological activity of the latter [18]. However, few reports to date have investigated the role of chitol oligosaccharidesacharide as an elicitor in improving the quality of soybean sprouts, especially their phytochemicals, enzymatic, and antioxidant activities. In the present study, we evaluated the elicitor effects of chitol oligosaccharidesacharide on phytochemicals, enzymatic, and antioxidant activities of germinated soybean. To the best of our knowledge, this is the first report on the application of chitol oligosaccharidesacharide as an elicitor in improving the quality of soybean sprouts.