Isolation And Preliminary Fermentation Evaluation Of Butanol-producing Strains Using Xylose As Carbon Source

Butanol possesses many favourable properties such as high energy density,less hygroscopicity and volatility,low corrosive and vapor pressure and so on,which makes it become one of hotspots in the global energy field.Butanol production via fermentation has received extensive concern as biofuel due to its sustinable and uncontamination,which also is regarded as additives of cosmetics and pharmaceutical intermediates due to its production safety.Thus,butanol production by Clostridia fermentation has regained widely conncered.On the other hand,lignocellulosic biomass has attracted increasing interest due to its low-cost and abundance,which could be degraded to monosaccharide?mainly glucose and xylose?for fermentation.However,the capicity of directly utilizing glucose of most butanol-producing strains is currently better than that of xylose,which greatly decreases the utilization rate of lignocellulosic biomass.Thus,isolation of stable butanol-producing strains that could efficiently and stably utilize xylose to produce butanol is significant to these strains in the industrial application of lignocellulose hydrolysates.Strain CH5 is capable of producing butanol,isopropabol,and a small amount of ethanol from xylose was isolated from soil samples,which is belong to natural IBE?isopropanol-butanol-ethanol?producers that exhibit only a few strains currently.Firstly,we evaluated the fermentation performance of the strain,and it produced the highest butanol and total solvent production,9.30 g/l and 11.87 g/l,respectively,which was equal to the highest butanol production reported currently using natural IBE producers.Then,it was found to sort to Clostridium beijerinckii by morphological observation/acetone identification and 16S rRNA identification experiments.Compared with traditional ABE fermenation,One of the products of IBE fermertation was isopropanol instead of acetone.In order to improve butanol production from xylose,strain CH5 was subject to NTG mutagenesis.And 5 mutants were obtained and then evaluated their fermentation performance and genetic stability.After 11 times'successively transferred to fresh medium,mutant strain 51543 exhibited the best fermentation performance and genetic stability.Then the carbon source spectrum of mutant 51543were investigated,and the result showed that this strain could utilize extensive carbon source for butanol production.When 2%cellobiose was used as carbon source,mutant 51543 could produce 7.23 g/l butanol which was the highest value of the current reported results with 2%cellobiosse as carbon source.Meanwhile,the fermentation conditions(the initial conccentration of xylose,temperture,pH,Mg²⁺,rotating speed)were optimized.The fermentation experiment of mutant 51543 was performed under optimized conditions,and butanol and solvent production was 11.79g/l and 15.81 g/l,respectively,indicating that mutant 51543 has the potential to utilize hydrolysate of lignocellulose for butanol production.