title: Biomass pyrolysis liquid to citric acid via 2-step bioconversion.
abstract: BACKGROUND
  The use of fossil carbon sources for fuels and petrochemicals has serious impacts on our environment and is unable to meet the demand in the future. A promising and sustainable alternative is to substitute fossil carbon sources with microbial cell factories converting lignocellulosic biomass into desirable value added products. However, such bioprocesses require tolerance to inhibitory compounds generated during pretreatment of biomass. In this study, the process of sequential two-step bio-conversion of biomass pyrolysis liquid containing levoglucosan (LG) to citric acid without chemical detoxification has been explored, which can greatly improve the utilization efficiency of lignocellulosic biomass.
  
  
  RESULTS
  The sequential two-step bio-conversion of corn stover pyrolysis liquid to citric acid has been established. The first step conversion by Phanerochaete chrysosporium (P. chrysosporium) is desirable to decrease the content of other compounds except levoglucosan as a pretreatment for the second conversion. The remaining levoglucosan in solution was further converted into citric acid by Aspergillus niger (A. niger) CBX-209. Thus the conversion of cellulose to citric acid is completed by both pyrolysis and bio-conversion technology. Under experimental conditions, levoglucosan yield is 12% based on the feedstock and the citric acid yield can reach 82.1% based on the levoglucosan content in the pyrolysis liquid (namely 82.1 g of citric acid per 100 g of levoglucosan).
  
  
  CONCLUSIONS
  The study shows that P. chrysosporium and A. niger have the potential to be used as production platforms for value-added products from pyrolyzed lignocellulosic biomass. Selected P. chrysosporium is able to decrease the content of other compounds except levoglucosan and levoglucosan can be further converted into citric acid in the residual liquids by A. niger. Thus the conversion of cellulose to citric acid is completed by both pyrolysis and bio-conversion technology.
authors.affiliation: Department of Environmental and Municipal Engineering, Henan University of Urban Construction, Pingdingshan, 467036, China. yangzg1@126.com.|Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China. yangzg1@126.com.
authors.forename: Zhiguang
authors.initials: Z
authors.lastname: Yang
authors.affiliation: Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China. zhbai@rcees.ac.cn.
authors.forename: Zhihui
authors.initials: Z
authors.lastname: Bai
authors.affiliation: Department of Environmental and Municipal Engineering, Henan University of Urban Construction, Pingdingshan, 467036, China. 13592189988@126.com.
authors.forename: Hongyan
authors.initials: H
authors.lastname: Sun
authors.affiliation: Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China. yuzs@ucas.ac.cn.
authors.forename: Zhisheng
authors.initials: Z
authors.lastname: Yu
authors.affiliation: Department of Environmental and Municipal Engineering, Henan University of Urban Construction, Pingdingshan, 467036, China. 1490819295@qq.com.
authors.forename: Xingxing
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Environmental and Municipal Engineering, Henan University of Urban Construction, Pingdingshan, 467036, China. gyifei@163.com.
authors.forename: Yifei
authors.initials: Y
authors.lastname: Guo
authors.affiliation: Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China. hxzhang@rcees.ac.cn.
authors.forename: Hongxun
authors.initials: H
authors.lastname: Zhang
mesh_terms: D001234:Aspergillus niger / Q000254:growth & development*; D018533:Biomass; D019149:Bioreactors; D019343:Citric Acid / Q000378:metabolism*; D008031:Lignin / Q000737:chemistry*; D020075:Phanerochaete / Q000254:growth & development*; D003313:Zea mays / Q000737:chemistry*
chemical_list: C036909:lignocellulose; D019343:Citric Acid; D008031:Lignin