1 Scientific RepoRts | 6:31662 | DOI: 10.1038/srep31662 www.nature.com/scientificreports Green bean biofortiication for Si through soilless cultivation: plant response and Si bioaccessibility in pods Francesco Fabiano Montesano 1 , Massimiliano D’Imperio 1 , Angelo parente 1 , Angela Cardinali 1 , Massimiliano Renna 1,2 & Francesco Serio 1 Food plants biofortiication for micronutrients is a tool for the nutritional value improvement of food. Soilless cultivation systems, with the optimal control of plant nutrition, represent a potential efective technique to increase the beneicial element content in plant tissues. Silicon (Si), which proper intake is recently recommended for its beneicial efects on bone health, presents good absorption in intestinal tract from green bean, a high-value vegetable crop. In this study we aimed to obtain Si biofortiied green bean pods by using a Si-enriched nutrient solution in soilless system conditions, and to assess the inluence of boiling and steaming cooking methods on Si content, color parameters and Si bioaccessibility (by using an in vitro digestion process) of pods. The Si concentration of pods was almost tripled as a result of the biofortiication process, while the overall crop performance was not negatively inluenced. The Si content of biofortiied pods was higher than unbiofortiied also after cooking, despite the cooking method used. Silicon bioaccessibility in cooked pods was more than tripled as a result of biofortiication, while the process did not afect the visual quality of the product. Our results demonstrated that soilless cultivation can be successfully used for green bean Si biofortiication. Plant biofortiication for micronutrients is arising increasing interest as a tool to improve the nutritional value of food plants, in the framework of the current worldwide challenge to produce, in a sustainable way, more and better food 1 . Two basic approaches can be adopted for biofortiication: i) increase of nutrient (micro and/or macronutrient) content in food plants 2,3 ; ii) reduction of antinutritional factors, such as phytates and oxalates (compounds able to reduce the bioavailability of nutrients) 4 . Both approaches can be achieved through diferent mechanisms, such as conventional plant breeding, genetic engineering and agronomic procedures 4 . Silicon (Si) is a general mineral component present in many food plants, including cereals, fruit, vegetables and legumes 5 . he Si content in plant tissues is generally related with species 6,7 . Its absorption in the intestinal tract is related to the food source. As an example, it is well absorbed from alcohol-free beer (64% of dose) and green beans (44%); in contrast, it is poorly absorbed (4%) from bananas 5 . Regarding nutritional aspects, Si intake is positively associated with promotion of bone formation, increase of bone mineral density in men and prom- enopausal women 8–10 . Several in vitro studies were performed in order to determine the plausible Si mechanism of action on bone 11 . Authors reported that Si, in in vitro studies, improved diferent parameters, such as cell proliferation, alkaline phosphatase activity and osteocalcin, and that Si increases cell type I collagen, in the osteosarcoma cell line MG-63 and the osteoblastic cell line HCC1 8,12 . Recent in vivo and epidemiological evidences indicate that nutri- tional intakes of Si are beneicial for bone health in humans 9,13 . Nielsen (2006) 14 suggests that an adequate intake, able to improve of bone health, might be between 10 and 25 mg∙day -1 . Although Si is generally not considered to be essential for higher plants 15 , its availability very signiicantly improves plant itness in nature and increases agricultural productivity 16,17 . Under an horticultural point of view, previous research focused on the role of Si in inducing protection against biotic stress 18 , and in alleviating the 1 Institute of Sciences of Food Production, CNR – National Research Council of Italy, Via G. Amendola, 122/O–70126 Bari, italy. 2 Department of Agricultural and Environmental Science – University of Bari Aldo Moro, Via Amendola, 165/ A–70126 Bari, Italy. Correspondence and requests for materials should be addressed to M.D. (email: massimiliano. dimperio@ispa.cnr.it) or F.S. (email: francesco.serio@ispa.cnr.it) received: 16 April 2016 accepted: 21 July 2016 Published: 17 August 2016 OPEN