搅拌转速和通风量对里氏木霉发酵β-甘露聚糖酶的影响

Effect of agitation speed and aeration rate on fermentation synthesis ofβ-mannanase with Trichoderma reesei

发酵液中溶解氧浓度是好氧发酵过程中反映氧传质效率的综合指标,维持发酵液适宜的溶解氧浓度是实现好氧发酵成功的关键所在,搅拌转速和通风量是影响发酵液溶解氧浓度的重要参数。笔者研究了在3 L发酵罐中搅拌转速和通风量对里氏木霉发酵合成β-甘露聚糖酶的影响。试验结果表明,里氏木霉发酵β-甘露聚糖酶时搅拌转速对氧传质效率的影响大于通风量。以质量浓度为1 g/L的葡萄糖和21.95 g/L的微晶纤维素为碳源发酵合成β-甘露聚糖酶,当搅拌转速450 r/min、通风量0.3 m^3/(m^3·min)时,发酵过程中溶解氧浓度保持在20%以上,发酵120 h,β-甘露聚糖酶活力、β-甘露糖苷酶活力和菌体质量浓度达到最大值3.92 U/m L,0.033U/m L和6.56 g/L。因此,发酵过程中溶解氧浓度维持在20%以上可获得较高的β-甘露聚糖酶活力。

Trichoderma reesei is a kind of microorganism that can secrete enzymes（ cellulase,hemicellulase,β-mannanase etc.） by aerobic fermentation with carbon sources,nitrogen source,and nutritive salt. For aerobic fermentation,the concentration of dissolved oxygen of fermentation broth is a comprehensive index to reflect the oxygen transfer efficiency. Meanwhile,maintaining a suitable concentration of dissolved oxygen in the fermentation broth is important to aerobic fermentation. During the fermentation process,the agitation speed and the aeration rate are both important parameters for oxygen transferring. In this study,the effects of the agitation speed（ 100-500 r/min） and the aeration rate（ 0. 2-1. 0 m^3/（ m^3·min）） on the production of β-mannanase by T. reesei were investigated in a 3 L fermentor. Specifically,the β-mannanase activity,β-manosidase activity and biomass were investigated when different agitation speed and aeration rate were carried out. The results showed that both the increased agitation speed and aeration rate could lead to higher oxygen transfer efficiency. However,the effect of agitation speed on oxygen transfer efficiency was greater than that of aeration rate. With the fermentation conditions for 1 g/L of glucose and 21. 95 g/L of microcrystalline cellulose as carbon sources at 450 r/min of agitation rate and 0. 3 m^3/（ m^3·min） of aeration rate for120 h,the dissolved oxygen tension can be remained above 20% during fermentation process. Accordingly,T. reesei could produce the β-mannanase with maximal β-mannanase activity,β-manosidase activity and biomass of 3. 92 U/m L,0. 033 U/m L and 6. 56 g/L,respectively. Therefore,it can be concluded that higher β-mannanase activity can be obtained when the dissolved oxygen tension is maintained at more than 20% in the fermentation process.