Currently available commercial enzyme preparations are limited in number and composition and have generally been optimized for acid-pretreated stover from maize and other grasses.
However, lignocellulosic feedstocks for sugar production include a variety of biomass: woody biomass such as softwood and hardwood, waste paper; non-wood biomass such as grass stovers (e.g., maize, sorghum, switchgrass or Miscanthus); and other biomass materials such as corn cobs, dried distillers’ grains solubles. All these biomass have different chemical composition, which will response differently to different pretreatments (e. acidic, basic, or oxidation), resulting in pretreated biomass with different chemical composition, even sugar composition. Therefore a general enzyme cocktail may work well for one type biomass or one type of pretreated biomass but not efficiently for other biomass. For example, for grass biomass with branchy arabinose and glucuronic acid, it may need GH10 endo-xylanase, a-arabinosidase, and a-glucuronidase. For woody biomass, in addition to the key endo-and exo-glucanases and endo-xylananse, it may need ferulate esterase and beta-mannanase. For acid pretreatment at a temperature >160 C, some of biomass hemicelluloses will be removed but some lignin may condense or re-deposit on fiber surface; while alkaline pretreatment will delignify but may have hemicelluloses re-deposited on the fiber surface. All of these will impact the efficiency of enzymatic hydrolysis and may require specifically modified enzyme cocktails. Therefore, a modified “customized” enzyme cocktail is more appropriate to adapt the spectrum of biomass and pretreatment combination for target hydrolysis.
A good research paper presents a study on this issue.
No comments:
Post a Comment