Study On Bamboo Shell Hydrolysate For Producing Of Xylitol By Fermentation

Bamboo shoots are lint production in Southern provinces,processing bamboo shoots will produce about one million tons of bamboo shell every year.And bamboo shells have largely been discarded.In fact,bamboo shells are rich in hemicellulose,it would be good material to produce xylose and xylitol.In order to study the feasibility of bamboo shell hydrolyzate fermentation xylitol,we first optimize the bamboo shell hemicellulosic hydrolysate,then use bamboo shell hydrolyzate as the source of xylose,screen strain which can produce xylitol,and mutagenic and optimize its conditions.The results are as follows:1?The optimum hydrolysis craft was determined according to single factor and orthogonal experiments.The optimal hydrolysis condition established by perpendieular design is sulfuric acid concentration 1%,reaction time1.5 h,hydrolysis temperature 120?,liquid to solid ratio?g/mL?1:9.Under the condition,xylose yield was?28.99±1.26?g/L.2?Using natural screening methods and xylose as sole carbon source,we screened 30 xylitol-producing strain from soil samples and moldy bamboo shell.Among 30 strains,number 3 strain had highest capacity to produce xylitol,xylitol conversion rate was?45.26±1.21?%.3?We used UV mutagenesis and chemical mutagenesis to mutagenize No.3 strain,respectively.UV mutagenesis results showed that:the best dilution was 10^-4,UV mutagenesis optimal exposure time was150s.Finally we got the highest xylitol production mutant strain ZT15 by three UV mutagenesis,which xylitol yield was?8.76±0.09?g/L,xylitol conversion rate was?53.73±0.92?%.Comparing with the original strain xylitol conversion rate increased 8.47%,revealed better genetic stability in five generations.The sodium nitrite chemical mutagenesis results showed that:the best diluted time for 10^-5,sodium nitrite mutagenesis best time for 5min.Through the three rounds sodium nitrite mutagenesis got the highest xylitol strain mutantions HT5,which xylitol yield?8.26±0.05?g/L,xylitol conversion rate?50.79±0.81?%,increasing 5.53%compared with the original strain,revealing better genetic stability in five generations.4?Use ZT15 as the original strain by single factor and orthogonal experiment to optimize the fermentation conditions and xylitol fermentation medium ingredients.The best condition:initial carbon concentration for 20 g/L,peptone and yeast extract for 30 g/L,MgSO₄·7H₂O for 0.2 g/L,?NH₄?SO₄ for 15 g/L,speed 180 r/min,temperature 30?,liquid volume 120mL,inoculum 8%,pH 5.5,fermentation time 48h,standing for 24h.Under these conditions,the concentration of xylitol was?11.81±0.06?g/L,the conversion rate of xylitol was?68.46±0.71?%.