title: Comprehensive utilization of waste hemicelluloses during ethanol production to increase lactic acid yield: from pretreatment to fermentation.
abstract: BACKGROUND
  Reducing the cost of producing cellulosic ethanol is essential for the industrialization of biorefinery. Several processes are currently under investigation, but few of these techniques are entirely satisfactory in terms of competitive cost or environmental impact. In this study, a new ethanol and lactic acid (LA) coproduction is proposed. The technique involved addition of waste alkaline peroxide pretreated hydrolysate (mainly LA and hemicelluloses) to the reaction mixture after ethanol fermentation (mainly LA and xylose) to reduce the ethanol production cost.
  
  
  RESULTS
  The following processes were investigated to optimize LA production: no addition of hemicelluloses or hydrolysate, addition of recycled hemicelluloses, and addition of concentrated hydrolysate. The addition of concentrated hydrolysate at 48 hours, which resulted in a maximum LA concentration of 22.3 g/L, was the most environment-friendly and cost-effective process. After the improved fermentation, 361 mg LA and 132 mg ethanol were produced from 1 g of raw poplar wood. That is, the production of one gallon of ethanol produced $9 worth of LA.
  
  
  CONCLUSIONS
  The amount of LA produced from the pretreated hydrolysate and reaction mixture after ethanol fermentation cannot be underestimated. The recovery of hydrolysate rich in LA and hemicelluloses (or xylose) significantly improved LA yield and further reduced the ethanol production cost.
authors.affiliation: Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing, 100083 China.
authors.forename: Liming
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing, 100083 China.
authors.forename: Tingting
authors.initials: T
authors.lastname: You
authors.affiliation: Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing, 100083 China.
authors.forename: Lu
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing, 100083 China ; MOE Key Laboratory of Wooden Material Science and Application, Beijing Forestry University, Beijing, 100083 China.
authors.forename: Mingfei
authors.initials: M
authors.lastname: Li
authors.affiliation: Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing, 100083 China ; MOE Key Laboratory of Wooden Material Science and Application, Beijing Forestry University, Beijing, 100083 China.
authors.forename: Feng
authors.initials: F
authors.lastname: Xu
keywords: Alkaline peroxide pretreatment; Cost-effective; Ethanol; Hemicelluloses; Lactic acid