Optimal Condition Of Cellwall Breaking For Yeast Culture And Its Effect On Substrate Fermentation

A study was carded out to investigate the effect of liquid cultivation in which yeast cell wasbroken on rumen fermentation and fiber digestibility.In experiment 1, conditions of cell-wall breaking with enzymatic and ultrasionic methodswas optimized. A 3×3 orthogonal experimental design was used to investigate the effect of amountof enzyme, temperature and time on cell-wall breaking for enzymatic method. A L9 (3⁴)orthogonal experimental design was also used to investigate the effect of power, the end diameterof horn and ultrasonic time on cell-wall breaking for ultrasionic method. At the same time, theeffect of cell-wall breaking on the content of vitamin was evaluated. In experiment 2, effect ofdifferent liquid cultivation in which yeast cell was broken on modeling rumen fermentation wasstudied. The experiment were distributed into 5 treatments: (1)addition with liquid cultivation inwhich yeast cell was broken by autolysis method (YC1); (2)addition with liquid cultivation inwhich yeast cell was broken by ultrasionic method (YC2); (3)addition with liquid cultivation inwhich yeast cell was broken by Lysozyme (YC3); (4)addition with liquid cultivation in which yeastcell was broken by Snailase (YC4); (5)control ration without yeast culture. The activities of CMCenzyme, concentration of ammonia, pH and gas production were assayed at the time 0h, 2h, 4h, 6h,8h after fermentation. In experiment 3, the trial in vitro was studied to compare the effect ofdifferent liquid cultivation in which yeast cell was broken on the degradation of DM,NDF andADF. The trial is the same with experiment 2. The DM, NDF and ADF were assayed at the time 6h,12h, 24h, 36h, 48h, 60h after fermentation. The concrete trials and results as follows:Optimization of cell-wall breaking:The best condition for cell-wall breaking was determined on the basis of the breakage rate andthe content of vitamin after yeast cell was broken. The best conditions for cell-wall breaking withenzymatic method were as list: the amount of enzyme was 12mg/ml, cell wall broken at 50℃for6h for Lysozyme; the amount of enzyme was 12mg/ml, cell wall broken at 35℃for 6h for Snailase.The best conditions for cell-wall breaking with ultrasonic method were as list: power was 400W,the end diameter of horn was 15mm, and ultrasonic time was 10min under condition of ice bath.The content of vitamin in yeast culture with enzyme method was higher than the content of vitaminin yeast culture with ultrasionic method (P＜0.05).Effect of different broken liquid cultivation in which yeast cell was broken on modeling rumenfermentation:The result indicated that YC3 and YC4 increased the activities of CMC enzyme at 2-8h after fermentation (P＜0.05). Liquid cultivation in each trial all decreased the concentration of ammonia,compared with the control. YC3 and YC4 decreased the concentration of ammonia significantly(P＜0.05), compared with YC1 and YC2.Liquid cultivation in each trial all had trends of stabilizingpH in rumen (P＞0.05), compared with the contral. Liquid cultivation in each trial all increased gasproduction (P＜0.05), and decreased methane (CH₄) production significantly (P＜0.05), comparedwith the control.Effect of different liquid cultivation in which yeast cell was broken on the degradation of DM,NDF and ADF:The result showed that there was no significant effect of each liquid cultivation on DM inthe fermentation (P＞0.05). The difference of the degradation ratio of NDF was no significantbetween liquid cultivation in each trial all and the control not significant (P＞0.05) at 6h to 24h afterfermentation. YC3 and YC4 at 36h, 48h, 60h after fermentation, YC1 at 36h, 60h after fermentationand YC2 at 60h after fermentation increased degradation ratio of NDF significantly (P＜0.05),compared with control. YC3 and YC4 at 12h, 24h, 48h, 60h after fermentation,YC1 at 60h afterfermentation and YC2 at 48h, 60h after fermentation increased degradation ratio of ADF (P＜0.05),compared with the control.By the above analysis: on account of the breakage rate and the content of vitamin and cost,effect of cell-wall breaking addition Lysozyme was optimal.liquid cultivation in which yeast cellwas broken could increase vogor of cellase, decrease ammonia, stabilize pH in rumen, increasetotal gas and decrease CH₄ production; increase degradation ratio ofDM, CP, NDF.