本文選題：乳鏈菌肽 + 小麥秸稈��； 參考：《陜西科技大學(xué)》2017年碩士論文

【摘要】：乳鏈菌肽(Nisin)是由乳酸鏈球菌或乳酸乳球菌發(fā)酵產(chǎn)生的一類陽離子疏水性的小分子多肽化合物,屬于微生物抗菌肽,具有無毒、不產(chǎn)生抗藥性等特點,被認(rèn)為是安全綠色的食品防腐劑。近年來乳鏈菌肽被認(rèn)為是非常具潛力的抗生素替代品,在醫(yī)藥行業(yè)中有廣泛的應(yīng)用前景。秸稈作為無限可再生的生物質(zhì)資源,來源廣泛、價格低廉,但對其不恰當(dāng)?shù)奶幚頃斐蓢?yán)重的環(huán)境污染。利用秸稈原料生物煉制乳鏈菌肽,為乳鏈菌肽的生產(chǎn)提供了一種新的原料,使秸稈資源得到有效利用,增加秸稈原料生物煉制的產(chǎn)品。本文以小麥秸稈為原料,研究秸稈的預(yù)處理、酶解、秸稈水解液培養(yǎng)基組成以及分批發(fā)酵過程控制等環(huán)節(jié)的技術(shù)參數(shù),主要研究內(nèi)容和實驗結(jié)果如下:(1)研究影響預(yù)處理的各因素,采用正交實驗對堿預(yù)處理小麥秸稈的條件進(jìn)行優(yōu)化,并對其進(jìn)行表征。研究結(jié)果表明,堿濃度和時間對預(yù)處理效果影響十分顯著,且小麥秸稈預(yù)處理最佳條件為:反應(yīng)溫度50℃,料液比1:40,堿濃度3.5%,反應(yīng)時間30 h。在此條件下,還原糖得率為34.35%。通過對預(yù)處理前后的小麥秸稈進(jìn)行掃描電鏡、X衍射以及紅外光譜分析,得出堿預(yù)處理小麥秸稈可以脫除秸稈中的絕大部分木質(zhì)素和少部分的半纖維素,并使纖維素發(fā)生潤脹,使致密的小麥秸稈表面出現(xiàn)一些裂縫和裂痕,從而使得纖維素酶與纖維素的接觸面積增加,促進(jìn)酶解反應(yīng)的進(jìn)行。(2)研究影響復(fù)合酶酶解效果的各因素,使用Box-Behnken實驗來優(yōu)化酶解條件,構(gòu)建響應(yīng)面模型。通過響應(yīng)面分析得出最優(yōu)酶解條件為:復(fù)合酶的添加量32.5 mg/g,反應(yīng)時間23.87 h,pH值4.57,溫度50.9℃,料液比1:28.6,在此條件下,還原糖得率為51.22%,水解液中還原糖含量為37 g/L。成功構(gòu)建響應(yīng)面模型,且響應(yīng)面模型的準(zhǔn)確率達(dá)91.24%。(3)對小麥秸稈水解液培養(yǎng)基的氮源、磷源以及營養(yǎng)物質(zhì)的種類和含量進(jìn)行研究,采用正交實驗對其進(jìn)行優(yōu)化。結(jié)果表明玉米漿的添加量對發(fā)酵生產(chǎn)乳鏈菌肽有著顯著的影響,適于嗜熱乳鏈球菌6032發(fā)酵生產(chǎn)乳鏈菌肽的水解液培養(yǎng)基組成為:酵母膏13 g/L,磷酸氫二鉀4.5 g/L,乙酸鈉5 g/L,檸檬酸氫二銨2 g/L,硫酸鎂0.58 g/L,硫酸錳0.24 g/L,玉米漿32%,還原糖含量37 g/L的小麥秸稈水解液。發(fā)酵所得乳鏈菌肽效價為5752 IU/mL。(4)研究影響發(fā)酵條件的各因素,采用Box-Behnken實驗來優(yōu)化發(fā)酵條件,建立響應(yīng)面模型。對響應(yīng)面進(jìn)行分析得出發(fā)酵過程中發(fā)酵液的pH值對發(fā)酵生產(chǎn)乳鏈菌肽有著十分顯著的影響,轉(zhuǎn)速對發(fā)酵生產(chǎn)乳鏈菌肽的影響次之,溫度和初始pH值對發(fā)酵的影響較小,并得出最優(yōu)發(fā)酵條件為:發(fā)酵初始pH值7,發(fā)酵過程中發(fā)酵液pH值維持在5.6,發(fā)酵溫度30℃,轉(zhuǎn)速為49 r/min,在此條件下,Nisin效價可達(dá)到6172 IU/mL。并對構(gòu)建的響應(yīng)面模型進(jìn)行實驗驗證,模型的重現(xiàn)率達(dá)96.36%。
[Abstract]:Nisin is a kind of small cationic hydrophobic polypeptide produced by the fermentation of Streptococcus lactis or Lactococcus lactis. Food preservatives considered safe and green. In recent years, nisin has been considered as a potential substitute for antibiotics, and has a wide application prospect in the pharmaceutical industry. Straw, as an unlimited renewable biomass resource, has a wide range of sources and low price, but improper treatment will cause serious environmental pollution. A new raw material for the production of nisin is provided by biological refining of the raw material of straw, which can make the straw resource be effectively utilized and increase the product of biological refining of the raw material of straw. In this paper, wheat straw was used as raw material to study the technical parameters of straw pretreatment, enzymatic hydrolysis, composition of straw hydrolysate medium and control of batch fermentation process. The main contents and experimental results are as follows: (1) the factors affecting pretreatment were studied. The conditions of alkali pretreatment of wheat straw were optimized and characterized by orthogonal experiment. The results showed that the effect of alkali concentration and time on the pretreatment was very significant, and the optimum conditions of wheat straw pretreatment were as follows: reaction temperature 50 鈩，

本文編號：1994200