ABSTRACT
Pretreatment is the crucial step to overcome the biorecalcitrance of lignocellulose to achieve efficient bioconversion of cellulose into fermentable sugars and then to fermentation products such as ethanol [1-6]. Among various pretreatment methods, dilute sulfuric acid pretreatment is considered to be the one with potential commercial applications [7-12]. The major disadvantages of dilute acid pretreatment include relatively massive acidic waste water generation caused by low solids (lignocellulosic feedstock) content, loss of fermentable sugars during the solids/liquid separation after pretreatment, and relatively high inhibitor compounds generation [13]. To overcome these disadvantages, recent studies on dilute acid
pretreatment have tried to increase the feedstock content of lignocellulose solids as high as possible [14-16]. One example in our previous study was a dry dilute acid pretreatment of corn stover, in which the solids content in the pretreatment was fed to an extreme high of up to 70% of the total feedstock [17] and successfully applied to production of ethanol, lipid, and lactic acid from corn stover [18-21]. This dilute acid pretreatment was called a ‘dry’ method, because both the corn stover feedstock and the pretreated corn stover product were ‘dry’ with no free water generation during the pretreatment, while the inhibitor generation was kept at a low level. In this way, the three major disadvantages of dilute acid pretreatment could be overcome: dry-in and dry-out thus no waste water was generated, dry pretreated product thus no solids/liquid separation was needed, and low inhibitor generation maintained a high pretreatment efficiency.
