李肖 陳永成 黃嶸崢 許平珠 張凡凡 馬春暉
doi:10.6048/j.issn.1001-4330.2024.03.010
摘? 要:【目的】研究向日葵副產(chǎn)物中優(yōu)勢(shì)乳酸菌和纖維素分解菌的生理生化特征,為向日葵副產(chǎn)物發(fā)酵飼料提供基礎(chǔ)。
【方法】對(duì)向日葵副產(chǎn)物表面附著優(yōu)勢(shì)乳酸菌及纖維素分解菌進(jìn)行分離、提取鑒定,并分析優(yōu)勢(shì)菌種生理生化特征。
【結(jié)果】分離出3株乳酸菌和4株纖維素分解菌。得到3株乳酸菌均為蒙氏腸球菌(Enterococcus mundtii)。4株纖維素分解菌中,菌株Z2和Z13為貝萊斯芽孢桿菌(Bacillus velezensis),X14為阿氏芽孢桿菌(Bacillus aryabhattai),X4與解淀粉芽孢桿菌(Bacillus amyloliquefaciens)。3株乳酸菌在4、10、30和45℃及3%和6.5%的NaCl條件下生長(zhǎng)良好,在pH 3.5~9可生長(zhǎng),在pH 3環(huán)境下不生長(zhǎng);4株纖維素分解菌中透明圈直徑(D)/菌落直徑(d)比值和酶活性按大小排序均為解淀粉芽孢桿菌>貝萊斯芽孢桿菌>阿氏芽孢桿菌。
【結(jié)論】蒙氏腸球菌具有較強(qiáng)耐鹽能力且溫度適應(yīng)范圍廣,但其產(chǎn)酸能力明顯弱于植物乳桿菌(Lactobacillus plantarum);4株纖維素分解菌在CMC糖化酶活力、濾紙酶活性及向日葵副產(chǎn)物的實(shí)際失重率中,接種解淀粉芽孢桿菌效果最優(yōu)。
關(guān)鍵詞:向日葵副產(chǎn)物;乳酸菌;纖維素分解菌;分離;鑒定;酶活性
中圖分類(lèi)號(hào):S188??? 文獻(xiàn)標(biāo)志碼:A??? 文章編號(hào):1001-4330(2024)03-0607-08
收稿日期(Received):
2023-08-05
基金項(xiàng)目:
農(nóng)業(yè)農(nóng)村部:國(guó)家現(xiàn)代農(nóng)業(yè)產(chǎn)業(yè)技術(shù)體系項(xiàng)目(CARS);新疆維吾爾自治區(qū)優(yōu)質(zhì)飼草產(chǎn)業(yè)技術(shù)體系項(xiàng)目(2022XJSC-Z-02)
作者簡(jiǎn)介:
李肖(1998-),男,新疆伊犁人,碩士研究生,研究方向?yàn)轱暡菁庸づc生產(chǎn),(E-mail)744364871@qq.com
通信作者:
張凡凡(1989-),男,新疆烏魯木齊人,副教授,博士,碩士生導(dǎo)師,研究方向?yàn)轱暡菁庸づc生產(chǎn),(E-mail)zhangfanfan@shzu.edu.cn
馬春暉(1966-),男,新疆哈密人,教授,博士,碩士生/博士生導(dǎo)師,研究方向?yàn)轱暡菁庸づc生產(chǎn),(E-mail)chunhuima@126.com
0? 引 言
【研究意義】向日葵(Helianthus annuus)為菊科向日葵屬的一年生經(jīng)濟(jì)作物,抗逆性強(qiáng)[1]。向日葵除籽實(shí)外剩余的副產(chǎn)物(葵稈、葵葉和葵盤(pán))營(yíng)養(yǎng)價(jià)值豐富[2],若合理利用可作為反芻動(dòng)物的飼料來(lái)源[3],能夠在一定程度上緩解局部飼草短缺壓力?!厩叭搜芯窟M(jìn)展】原料發(fā)酵過(guò)程中除底物有充足的碳源和氮源外,有益乳酸菌的數(shù)量是調(diào)控青貯的關(guān)鍵[4,5];當(dāng)發(fā)酵原料表面附著乳酸菌低于105 cfu/g FW時(shí),需要外源添加乳酸菌制劑來(lái)確保發(fā)酵品質(zhì)。在實(shí)際生產(chǎn)過(guò)程中采取的手段主要為同、異質(zhì)型乳酸菌聯(lián)合接種,以最大程度減少發(fā)酵損失,提高青貯飼料有氧穩(wěn)定性、減少二次發(fā)酵[6-7]。此外,纖維素的降解也是調(diào)控秸稈類(lèi)原料發(fā)酵的主要問(wèn)題,通過(guò)纖維素的降解不僅能夠?yàn)榘l(fā)酵底物提供更為充足的碳源,且能夠改善飼料品質(zhì),促進(jìn)家畜的利用效率[8]。當(dāng)前降解纖維素的方法有物理法、化學(xué)法和生物法等。其中物理法和化學(xué)法[9]在降解纖維素時(shí)不僅會(huì)造成環(huán)境污染且成本較高,而生物法降解纖維素的過(guò)程溫和無(wú)污染且成本較低。在實(shí)際生產(chǎn)中多采用外源添加纖維素酶降解青貯原料中的木質(zhì)纖維素,然而纖維素酶成本較高不能大規(guī)模用于生產(chǎn);可通過(guò)添加纖維素分解菌來(lái)替換纖維素酶以降低成本[10]。當(dāng)前,在自然界分離出的纖維素分解菌(細(xì)菌、真菌和放線菌等)多達(dá)200余種[11],其中真菌如木霉屬(Trichoderma sp)、青霉屬(Penicillium sp)和曲霉屬(Aspergillus sp)等多為耐酸菌,分泌胞外酶,但在缺氧的環(huán)境下酶活性會(huì)降低[10],細(xì)菌多產(chǎn)胞內(nèi)酶,抗逆性強(qiáng)且繁殖速度快[12],而放線菌在繁殖速度和降解纖維能力上均弱于細(xì)菌和真菌,但有著更強(qiáng)的適應(yīng)性[13]?!颈狙芯壳腥朦c(diǎn)】近年來(lái),對(duì)不同植物中的纖維素分解菌和優(yōu)勢(shì)乳酸菌進(jìn)行篩選,其中不乏篩選出一些優(yōu)質(zhì)乳酸菌和纖維素分解菌[14-18]。當(dāng)前對(duì)向日葵副產(chǎn)物中優(yōu)勢(shì)乳酸菌及纖維素分解菌的篩選未見(jiàn)相關(guān)報(bào)道。且向日葵副產(chǎn)物中纖維含量較高,是否附著纖維素分解菌目前尚不明確。需研究向日葵副產(chǎn)物中優(yōu)勢(shì)乳酸菌及分離鑒定其纖維素分解菌。有必要研究向日葵副產(chǎn)物中優(yōu)勢(shì)乳酸菌和纖維素分解菌的生理生化特征?!緮M解決的關(guān)鍵問(wèn)題】分離鑒定向日葵副產(chǎn)物植物表面的附生優(yōu)勢(shì)乳酸菌及其纖維素分解菌,篩選出向日葵青貯所用的優(yōu)質(zhì)乳酸菌和高產(chǎn)纖維素酶的纖維素分解菌菌株,為秸稈類(lèi)青貯原料的菌劑研發(fā)提供理論基礎(chǔ)。
1? 材料與方法
1.1? 材 料
所用向日葵副產(chǎn)物原料取自新疆阿勒泰地區(qū)哈巴河縣(48°4′50.77″N,86°23′58.77″E,海拔530 m)。待向日葵成熟收取籽實(shí)(成熟期)后,于2021年9月1日收割其副產(chǎn)物(葵稈、葵盤(pán)和葵葉),并短切至1~2 cm備用。
1.2? 方 法
1.2.1? 乳酸菌的分離鑒定
乳酸菌的分離、純化、生理生化鑒定:生長(zhǎng)速率和產(chǎn)酸速率的測(cè)定參照張玉琳等[6]方法;乳酸菌對(duì)碳源的利用測(cè)定參照凌代文[19]方法。3株菌株為乳酸球菌,測(cè)定的結(jié)果與植物乳桿菌(Lactobacillus plantarum,Gen bank No.MZ008357)進(jìn)行對(duì)比(命名為L(zhǎng)P1)。
乳酸菌菌種分子生物鑒定:將純化后的乳酸菌培養(yǎng)液按試劑盒說(shuō)明提取各菌株DNA,DNA提取試劑盒由北京全式金生物技術(shù)有限公司提供。PCR擴(kuò)增采用細(xì)菌通用引物
FA-27F:5′-GCAGAGTTCTCGGAGTCACGAAGAGTTTGATCCTGGCTCAG-3′;
RA-1495R:5′-AGCGGATCACTTCACACAGGACTACGGGTACCTTGTTACGA-3′。
反應(yīng)體系為(50 μL):DNA模板5 μL,引物27F和1 495R(10 μmol/L)各1 μL,2×MasterMix25 μL,ddH2O補(bǔ)足至50 μL。反應(yīng)程序?yàn)椋?5℃10 min,95℃30 s,60℃30 s,72℃45 s,30個(gè)循環(huán)。將PCR擴(kuò)增產(chǎn)物送往生工生物工程(上海)股份有限公司測(cè)序。
1.2.2? 纖維素分解菌的篩選鑒定
1.2.2.1? 菌種分子鑒定
準(zhǔn)確稱取10 g樣品,加入90 mL滅菌水后震蕩30 min(37℃)得到菌懸液(1∶10)。將菌懸液梯度稀釋后涂布羧甲基纖維素鈉(CMC-Na)瓊脂平板培養(yǎng),將形態(tài)和大小不同的菌落劃線純化后送至生工生物工程(上海)股份有限公司測(cè)序(所需引物為細(xì)菌通用引物,同乳酸菌菌種分子生物鑒定)。
1.2.2.2? 纖維素分解菌菌株酶活力
將纖維素分解菌菌種接種至PDA液體培養(yǎng)中擴(kuò)繁后涂布于羧甲基纖維素鈉(CMC-Na)瓊脂平板,倒置培養(yǎng)3~5 d(28℃)后劃線純化,再點(diǎn)接于CMC-Na瓊脂平板倒置培養(yǎng)5 d(28℃),用1%剛果紅染液染色后再用NaCl(1 mol/L)溶液去色,測(cè)量透明圈直徑和菌落直徑并計(jì)算其比值(D/d)[20],同時(shí)連續(xù)測(cè)定5 d濾紙酶(FPA)和羧甲基纖維素鈉(CMC-Na)活性[21]。
1.2.2.3? 纖維素分解菌菌種降解秸稈試驗(yàn)
將纖維素分解菌菌種接種于PDA液體培養(yǎng)基中擴(kuò)繁(28℃培養(yǎng)3 d),再分別接種于以向日葵副產(chǎn)物為唯一碳源的液體發(fā)酵培養(yǎng)基中,接種量為10%,每過(guò)5 d測(cè)定向日葵副產(chǎn)物(纖維)失重率,觀察25 d。纖維測(cè)定采用范式(Van Soest)洗滌法[22],秸稈失重率%=(初始重量-接種菌種后重量)/初始重量×100%。
1.3? 數(shù)據(jù)處理
采用Excel2020對(duì)所有試驗(yàn)數(shù)據(jù)進(jìn)行整理,采用Origin2021軟件繪圖,在GenBank中對(duì)16SrDNA序列進(jìn)行比對(duì),用MEGA8.0中的ClustalW對(duì)最近類(lèi)群的序列進(jìn)行多重比較分析,通過(guò)該軟件的鄰近法(Neighbor-Joining)構(gòu)建系統(tǒng)發(fā)育樹(shù),確定各菌株分類(lèi)地位[23]。
2? 結(jié)果與分析
2.1? 乳酸菌菌株的生理生化特性
研究表明,3株菌株的革蘭氏染色結(jié)果均為陽(yáng)性,觸酶試驗(yàn)為陰性。且所有菌株發(fā)酵葡萄糖產(chǎn)酸不產(chǎn)氣,為同型發(fā)酵乳酸菌。除X1菌株在4℃環(huán)境表現(xiàn)為弱生長(zhǎng)外,其他菌株均能正常生長(zhǎng)。此外,所有菌株均能在10、30和45℃及3%NaCl和6.5% NaCl正常生長(zhǎng)。所有菌株均能在pH 4~9生長(zhǎng),在pH 3.5呈弱生長(zhǎng),而pH 3明顯抑制了菌株的生長(zhǎng)。所有菌株對(duì)鼠李糖和蜜爾糖利用交弱,對(duì)松三糖不能利用,其余糖、醇均可利用,菌株LP1為植物乳桿菌L.plantarum。表1
2.2? 乳酸菌和纖維素分解菌菌株的基因序列
研究表明,3株乳酸菌與標(biāo)準(zhǔn)菌株的序列相似性均超過(guò)99.89%,將每種菌各選部分參考菌株構(gòu)建系統(tǒng)進(jìn)化樹(shù),與蒙氏腸球菌(Enterococcus mundtii)的進(jìn)化親緣度均為100%。3株乳酸菌株均為蒙氏腸球菌(Enterococcus mundtii)。菌株X12、X13、Z5在Genbank中的登錄號(hào)為MZ008631、OL98461、OM102992。表2~3
4株纖維素分解菌與標(biāo)準(zhǔn)菌株的序列相似性均超過(guò)了99.89%,Z2和Z13與貝萊斯芽孢桿菌(Bacillus velezensis)的進(jìn)化親緣度為100%,X14與阿氏芽孢桿菌(Bacillus aryabhattai)的進(jìn)化親緣度為100%,X4與解淀粉芽孢桿菌(Bacillus amyloliquefaciens)的進(jìn)化親緣度為100%。Z2和Z13為貝萊斯芽孢桿菌(Bacillus velezensis),X14為阿氏芽孢桿菌(Bacillus aryabhattai),X4與解淀粉芽孢桿菌(Bacillus amyloliquefaciens)。圖1
2.3? 乳酸菌菌株的產(chǎn)酸速率及生長(zhǎng)特性
研究表明,3株乳酸菌株均為蒙氏腸球菌。因此,隨機(jī)選擇3株乳酸菌株測(cè)定其產(chǎn)酸速率及生長(zhǎng)特性,并以植物乳桿菌(LP1)進(jìn)行對(duì)比。蒙氏腸球菌在0~10 h產(chǎn)酸速率較快,在10~24 h產(chǎn)酸速率逐漸變慢,植物乳桿菌的產(chǎn)酸速率在0~8 h較慢,8~14 h迅速下降,14 h后逐漸平緩,且植物乳桿菌的產(chǎn)酸速率在0~24 h均高于菌株X6、X7和X9。在培養(yǎng)4 h后蒙氏腸球菌進(jìn)入對(duì)數(shù)生長(zhǎng)期,14 h后進(jìn)入穩(wěn)定期,且在24 h內(nèi)未出現(xiàn)停滯期,植物乳桿菌在0~8 h生長(zhǎng)速率低于菌株X6、X7和X9,在18~24 h逐漸超越。圖2
2.4? 纖維素分解菌降解秸稈效果
研究表明,解淀粉芽孢桿菌(X4)透明圈直徑和菌落直徑及其比值(D/d)顯著大于阿氏芽孢桿菌和貝萊斯芽孢桿菌(P<0.05),阿氏芽孢桿菌顯著低于Z2、貝萊斯芽孢桿菌(P<0.05)。表3
隨著時(shí)間的上升,4株菌株的CMC糖化酶活和濾紙酶活性隨著培養(yǎng)時(shí)間的增加呈現(xiàn)先上升后降低的趨勢(shì),并在72 h左右酶活力達(dá)到峰值。其中菌株解淀粉芽孢桿菌的酶活性最高。
向日葵副產(chǎn)物失重率隨著時(shí)間的增加而上升,菌種解淀粉芽孢桿菌降解向日葵副產(chǎn)物效果最優(yōu),阿氏芽孢桿菌最差。圖3
3? 討 論
3.1? 向日葵副產(chǎn)物中乳酸菌生理生化特征
試驗(yàn)從向日葵副產(chǎn)物中篩選出的3株乳酸菌種均為蒙氏腸球菌(Enterococcus mundtii)。研究中,蒙氏腸球菌能夠利用除松三糖以外的糖,其中對(duì)鼠李糖和蜜二糖利用能力較弱,這與諸多研究結(jié)果一致[24-25]。優(yōu)質(zhì)乳酸菌應(yīng)具有較高的產(chǎn)酸
及耐酸能力,并且競(jìng)爭(zhēng)力強(qiáng),生長(zhǎng)旺盛。此外,蒙氏腸球菌能在4~45℃的環(huán)境下生長(zhǎng),且對(duì)高濃度的NaCl存在一定的耐受性,但在pH 3的環(huán)境
下很難生長(zhǎng)。部分同質(zhì)乳酸菌腸球菌(Enterococcus spp.)、片球菌(Pediococcus spp.)等在青貯發(fā)酵前期生長(zhǎng)迅速,產(chǎn)酸較快,實(shí)際生產(chǎn)中往往與植物乳桿菌(Lactobacillus plantarum)復(fù)合添加改善青貯品質(zhì)[6]。研究中蒙氏腸球菌在12 h內(nèi)的生長(zhǎng)及產(chǎn)酸速率高于植物乳桿菌,但在12 h后表現(xiàn)較差。研究中,在向日葵副產(chǎn)物中篩選出的3株菌種除蒙氏腸球菌外,并未篩選出其他乳酸菌種,其主要原因是植物原料未經(jīng)發(fā)酵導(dǎo)致其表面微生物附著單一,還可能是由于當(dāng)?shù)貧夂蚝秃0胃叨葘?duì)向日葵表面微生物種類(lèi)分布存在一定影響[26-27]。
3.2? 向日葵副產(chǎn)物中的纖維素分解菌酶活力
試驗(yàn)通過(guò)對(duì)4株進(jìn)行菌種分子生物鑒定,確定菌株Z2和Z13為貝萊斯芽孢桿菌(Bacillus velezensis),X14為阿氏芽孢桿菌(Bacillus aryabhattai),X4與解淀粉芽孢桿菌(Bacillus amyloliquefaciens)。研究發(fā)現(xiàn),透明圈直徑/菌落直徑(D/d)比值反映了菌種降解纖維素能力[28],3種纖維素分解菌菌株中解淀粉芽孢桿菌降解纖維能力最強(qiáng),測(cè)定3種菌株的CMC糖化酶活力和濾紙酶活性也得到了印證。在玉米秸稈中篩選出的解淀粉芽孢桿菌對(duì)木質(zhì)纖維素有著強(qiáng)降解作用[18],與研究結(jié)果一致。阿氏芽孢桿菌被發(fā)現(xiàn)可降解木質(zhì)素,但目前研究對(duì)象多為工業(yè)合成的木質(zhì)纖維素及化合物,很少被用于降解植物中的木質(zhì)纖維素[29],研究中阿氏芽孢桿菌對(duì)向日葵副產(chǎn)物存在一定的降解能力,但效果不強(qiáng),阿氏芽孢桿菌在3 d內(nèi)纖維素酶活性保持較低水平[30],與研究結(jié)果相似。貝萊斯芽孢桿菌不僅能產(chǎn)纖維素酶,還有一定的抑菌作用[31],研究也發(fā)現(xiàn)貝萊斯芽孢桿菌對(duì)纖維素降解有一定效果。此外,濾紙酶活性反映了纖維素酶中多種酶協(xié)同作用的總效果,CMC糖化酶活力則是外切β-1,4葡聚糖苷酶和內(nèi)切酶的活力總和。研究中4株菌種的CMC糖化酶活力菌高于濾紙酶活性,纖維素酶中各酶系的協(xié)同作用至關(guān)重要,某一類(lèi)酶活性的高低并不能完全證明其降解纖維素效果的強(qiáng)弱。聯(lián)合接種纖維素分解菌和布氏乳桿菌(Lactobacillus buchneri)可改善玉米秸稈青貯品質(zhì)[32]。
4? 結(jié) 論
4.1
蒙氏腸球菌為向日葵副產(chǎn)物表面附著優(yōu)勢(shì)乳酸菌,其雖具有較強(qiáng)的耐鹽能力和溫度適應(yīng)范圍,但其產(chǎn)酸能力明顯弱于植物乳桿菌,在后期調(diào)制向日葵青貯飼料須接種外源優(yōu)質(zhì)乳酸菌以滿足發(fā)酵需求。
4.2? 在向日葵副產(chǎn)物中篩選出1株解淀粉芽孢桿菌,1株阿氏芽孢桿菌和2株貝萊斯芽孢桿菌。其中,解淀粉芽孢桿菌降解纖維素能力最優(yōu)。
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Physiological and biochemical characteristics of dominant lactic acid bacteria and cellulolytic bacteria in sunflower By-Products
LI Xiao1,CHEN Yongcheng1,HUANG Rongzheng1,XU Pingzhu2,ZHANG Fanfan1,MA Chunhui1
(1. College of Animal Science and Technology,Shihezi University,Shihezi Xinjiang 832000,China.2.Xingjiang Xu zhihua Grassland Ecology Co.,Ltd,Habahe Xinjiang 836700,China)
Abstract:【Objective】 This study aims to provide a basis for fermented feeds by sunflower by-products.
【Methods】? The dominant lactic acid bacteria and cellulolytic bacteria attached to the surface of sunflower by-products were isolated,extracted and identified,and the physiological and biochemical characteristics of the dominant bacteria were analyzed.
【Results】? 3 strains of lactic acid bacteria and 4 strains of cellulolytic bacteria were isolated.The 3 strains of lactic acid bacteria obtained were Enterococcus mundtii.Among the 4 strains of cellulolytic bacteria,strains Z2 and Z13 were Bacillus velezensis,X14 was Bacillus aryabhattai,and X4 was Bacillus amyloliquefaciens.3 strains of lactic acid bacteria grew well under the conditions of 4,10,30 and 45℃,3% and 6.5% NaCl,grew at pH 3.5-9,and did not grow at pH3; among the 4 strains of cellulolytic bacteria,the ratio of transparent circle diameter(D)/colony diameter(d) and enzyme activity in order of size were Bacillus amyloliquefaciens > Bacillus velezensis > Bacillus aryabhattai.
【Conclusion】 Enterococcus mundtii has strong salt tolerance and a wide range of temperature adaptation,but its acid-producing ability is significantly weaker than that of Lactobacillus plantarum.In the actual weight loss rate of the product,the effect of inoculation with Bacillus amyloliquefaciens is the best.
Key words:sunflower byproduct; lactic acid bacteria; cellulolytic bacteria; isolation; identification; enzymatic activity
Fund projects:Ministry of Rural Agriculture:China Agriculture Research System (CARS);Xinjiang Uygur Autonomous Region High-quality forage industry technology system project(2022XJSC-Z-02)
Correspondence author: ZHANG Fanfan (1989-), male, from Urumqi, Xinjiang, Ph.D, associate professor, master tutor, research direction: forage production and processing,(E-mail)zhangfanfan@shzu.edu.cn
MA Chunhui (1966-), male, from Hami, Xinjiang, Ph.D, professor,doctoral supervisor, research direction: forage production and processing,(E-mail)chunhuima@126.com