l-(+) lactic acid production by Rhizopus oryzae using pretreated dairy manure as carbon and nitrogen source

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• 作者：J. Sun^a ; ^b ; ^{sunjianping@gmail.com} ; J. Zhu^b ; W. Li^c
• 关键词：Diary manure ; Pretreatment ; l-(+) lactic acid production ; pH value ; Morphology ; Ethanol
• 刊名：Biomass and Bioenergy
• 出版年：2012
• 出版时间：December, 2012
• 年：2012
• 卷：47
• 期：Complete
• 页码：442-450
• 全文大小：728 K

文摘

The optimal pretreatment condition for dairy manure further use obtained through the Box-Behnken experimental design was temperature 120?¡ãC, H₂SO₄ concentration 1.61 % and solid content 1 % , among which temperature was the key factor influencing the performance of pretreatment. Under this condition, dry dairy manure could produce 60.8 % of reducing sugar and 2.83 % of protein. The pretreated dairy manure was then used as the fermentation substrate for producing l-(+) lactic acid by Rhizopus oryzae without any supplement of additional carbon and nitrogen source. The results demonstrated that either l-(+) lactic acid or ethanol produced could reach the highest concentration and yield in two days. R. oryzae was able to utilize pretreated dairy manure to produce l-(+) lactic acid and the highest concentration and yield were 1210.02?mg?L^?1 and 40.09 % at pH 10, respectively, when ethanol as main byproducts was at a lowest level (74.64?mg?L^?1), whereas at acidic condition the concentration of ethanol could arrive at a higher level (648.15?mg?L^?1). The pH not only affected the production of l-(+) lactic acid and ethanol but also had an impact on the morphology of R. oryzae. At higher pH values, small and loose pellets of microorganism formed and produced more l-(+) lactic acid, while at low pH, filamentous mycelia were generated and less l-(+) lactic acid was produced. However, pH did not affect the C/N ratio in the fermentation broth since the ratio was observed to vary in a range from 12 to 15 during the experiment.