Abstract
An inhibitor-tolerance strain, Bacillus coagulans GKN316, was developed through atmospheric and room temperature plasma (ARTP) mutation and evolution experiment in condensed dilute-acid hydrolysate (CDH) of corn stover. The fermentabilities of other hydrolysates with B. coagulans GKN316 and the parental strain B. coagulans NL01 were assessed. When using condensed acid-catalyzed steam-exploded hydrolysate (CASEH), condensed acid-catalyzed liquid hot water hydrolysate (CALH) and condensed acid-catalyzed sulfite hydrolysate (CASH) as substrates, the concentration of lactic acid reached 45.39, 16.83, and 18.71 g/L by B. coagulans GKN316, respectively. But for B. coagulans NL01, only CASEH could be directly fermented to produce 15.47 g/L lactic acid. The individual inhibitory effect of furfural, 5-hydroxymethylfurfural (HMF), vanillin, syringaldehyde and p-hydroxybenzaldehyde (pHBal) on xylose utilization by B. coagulans GKN316 was also studied. The strain B. coagulans GKN316 could effectively convert these toxic inhibitors to the less toxic corresponding alcohols in situ. These results suggested that B. coagulans GKN316 was well suited to production of lactic acid from undetoxified lignocellulosic hydrolysates.
Highlights
Lignocellulosic biomass, especially agricultural and forest residues, is a potentially low-cost renewable resource of sugars for fermentation [1,2]
We showed that B. coagulans NL01 produces 18.2 g/L lactic acid from a steamexploded prehydrolysate [24], but this strain was inhibited when the hydrolysate was at a higher concentration
The surviving strains were challenged with the condensed dilute-acid hydrolysate (CDH) at concentrations increasing from 25% to 80%
Summary
Lignocellulosic biomass, especially agricultural and forest residues, is a potentially low-cost renewable resource of sugars for fermentation [1,2]. Its utilization could decrease the demand for petroleum and food raw materials and might alleviate the environmental pressure concerning CO2 emissions from fossil fuels. In China, corn stover is an agricultural residue that could be used for the production of biofuel and green chemicals [3]. The bioconversion and exploitation of this feedstock still face several technical obstacles at this time. Lignocelluloses are a matrix of cross-linked polysaccharide networks, which mainly consists cellulose, hemicelluloses and lignin [4]. The efficient utilization of pentose, mainly xylose, from hemicelluloses still remains a challenge for the economic feasibility of bioconversion
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