Abstract
BackgroundLignocellulosic biomass is an abundant and sustainable feedstock, which represents a promising raw material for the production of lactic acid via microbial fermentation. However, toxic compounds that affect microbial growth and metabolism are released from the biomass upon thermochemical pre-treatment. So far, susceptibility of bacterial strains to biomass-derived inhibitors still represents a major barrier to lactic acid production from lignocellulose. Detoxification of the pre-treated lignocellulosic material by water washing is commonly performed to alleviate growth inhibition of the production microorganism and achieve higher production rates.ResultsIn this study, we assessed the feasibility of replacing the washing step with integrated cellular adaptation during pre-culture of Bacillus coagulans MA-13 prior to simultaneous saccharification and lactic acid fermentation of steam exploded wheat straw. Using a seed culture pre-exposed to 30% hydrolysate led to 50% shorter process time, 50% higher average volumetric and 115% higher average specific productivity than when using cells from a hydrolysate-free seed culture.ConclusionsPre-exposure of B. coagulans MA-13 to hydrolysate supports adaptation to the actual production medium. This strategy leads to lower process water requirements and combines cost-effective seed cultivation with physiological pre-adaptation of the production strain, resulting in reduced lactic acid production costs.
Highlights
Lignocellulosic biomass is an abundant and sustainable feedstock, which represents a promising raw material for the production of lactic acid via microbial fermentation
Overall scheme of the pre‐adaptation strategy and simultaneous saccharification and fermentation (SSF) The underlying hypothesis of this work is that the fermentation performance, in terms of lactate yields on consumed glucose and lactate productivity, depends on the physiological state of B. coagulans MA-13 after seed cultivation
Anaerobic seed cultures were grown in hydrolysate-free medium (Fig. 1b) as well as in media supplemented with different amounts of hydrolysate (Fig. 1c)
Summary
Lignocellulosic biomass is an abundant and sustainable feedstock, which represents a promising raw material for the production of lactic acid via microbial fermentation. This may inconveniently compete with the supply of foods and feeds [7] To overcome this drawback, lignocellulosic biomass is an abundant and sustainable feedstock [8, 9], and a promising alternative source of raw material for LA production via microbial fermentation. After pre-treatment and saccharification, the fermentability of the biomass is generally hampered by toxic compounds, such as furfural, 5-hydroxymethyl furfural (HMF), and soluble phenolics, which are released from the biomass during the pre-treatment [18] These chemicals represent a major barrier in the development of production processes from lignocellulosic biomass [19], because they affect the fermentation rate by inhibiting microbial growth. The cost of this additional step is higher than its benefits [19, 20]; alternative strategies to alleviate inhibition need to be investigated
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