초록
<P><B>Abstract</B></P> <P>To effectively produce second-generation L-lactic acid (L-LA), for the first time, rice straw (RS) was pretreated by dilute ethylenediamine (EDA) and followed by fed-batch simultaneous saccharification and fermentation (SSF) under non-sterilized conditions. Specifically, the impact of pretreatment parameters included EDA concentration and pretreatment temperature on sugars and L-LA productions were evaluated. Results indicated that after pretreatment in 6% (w/v) EDA at 200 °C for 1 h and following the enzymatic hydrolysis, 42.25 g L<SUP>−1</SUP> of total monomer sugars was generated. By batch SSF, the maximized 63.5 ± 3.0 g L<SUP>−1</SUP>and 296.8 g Kg<SUP>−1</SUP> of L-LA can be obtained from the raw RS using <I>Bacillus coagulans</I> LA-15-2. Fed-batch SSF was further conducted and L-LA concentration of 92.5 g L<SUP>−1</SUP> was obtained in the final fermentation broth. Correspondingly, L-LA productivity and yield reached 2.01 g L<SUP>−1</SUP> h<SUP>−1</SUP> and 578.1 g Kg<SUP>−1</SUP>of the pretreated RS, respectively. This study provided a novel environmental-friendly method for L-LA production, which successfully avoided the usage of large amount of inorganic alkali in lignocellulose pretreatment stage.</P> <P><B>Highlights</B></P> <P> <UL> <LI> L-lactic acid production by SSF from ethylenediamine (EDA) pre-treated rice straw was studied. </LI> <LI> Effect of temperature and ethylenediamine concentration on rice straw pretreatment were optimized. </LI> <LI> The inhibition of dilute EDA on L-lactic acid fermentation was investigated. </LI> <LI> Fed-batch SSF was carried out in non-sterilized fermentation for high titer l-lactic acid production. </LI> <LI> 92.5 g L<SUP>−1</SUP> of L-LA was obtained with a yield of 578.1 g Kg<SUP>-1</SUP>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>