1 材料与方法
1.1 试验材料
1.2 试验方法
1.2.1 乳酸菌的分离与纯化
1.2.2 耐低糖乳酸菌的筛选
1.2.3 耐低糖乳酸菌乳酸产量和乳酸产率的测定
1.2.4 耐低糖乳酸菌对苜蓿汁液的发酵效果
1.2.5 ARTP诱变
1.2.6 突变菌株的初筛
1.2.7 突变菌株的复筛
1.2.8 突变菌株的分子生物学鉴定
1.2.9 突变菌株的遗传稳定性检验
1.2.10 突变菌株对苜蓿汁液的发酵效果
1.3 数据统计与分析
2 结果与分析
2.1 乳酸菌的初筛
2.2 耐低糖乳酸菌的筛选
表1 耐低糖乳酸菌在不同葡萄糖浓度培养基中培养48 h的pHTable 1 pH of low-sugar-tolerant lactic acid bacteria cultured in media with different glucose concentrations for 48 h |
| 菌株 Strains | 葡萄糖浓度 Glucose concentrations/(g/L) | 菌株来源 Sources of strains | ||||
|---|---|---|---|---|---|---|
| 20 | 2 | 0.2 | 0.02 | 0.002 | ||
| A1 | 3.86±0.01c | 5.61±0.02a | 6.37±0.05ab | 6.46±0.13b | 6.56±0.03b | 秸秆青贮 |
| A2 | 3.68±0.02e | 5.11±0.02d | 5.83±0.04c | 6.05±0.01c | 6.01±0.04d | 秸秆青贮 |
| A5 | 3.84±0.04cd | 5.34±0.07c | 6.38±0.03ab | 6.48±0.11b | 6.53±0.03b | 秸秆青贮 |
| A6 | 3.87±0.01bc | 5.43±0.01b | 6.32±0.04ab | 6.50±0.09b | 6.56±0.06b | 秸秆青贮 |
| A7 | 3.64±0.01e | 5.12±0.01d | 5.86±0.05c | 6.08±0.04c | 6.19±0.01c | 秸秆青贮 |
| A9 | 3.78±0.03d | 5.61±0.02a | 6.59±0.03a | 6.75±0.06a | 6.69±0.05a | 秸秆青贮 |
| B1 | 4.21±0.02a | 5.60±0.02a | 6.22±0.57b | 6.64±0.03a | 6.67±0.02a | 苜蓿鲜样 |
| B2 | 3.94±0.10b | 5.56±0.01a | 6.52±0.01ab | 6.65±0.02a | 6.66±0.01a | 苜蓿鲜样 |
| B4 | 4.16±0.02a | 5.56±0.01a | 6.52±0.02ab | 6.66±0.05a | 6.70±0.03a | 苜蓿鲜样 |
| C1 | 3.70±0.03e | 5.34±0.14c | 5.80±0.10c | 5.88±0.04d | 5.91±0.03e | 玉米青贮 |
同列数据肩标不同小写字母表示不同菌株间差异显著(P<0.05)。下表同。 | |
Values with different lowercase letter superscripts in the same column indicated significant difference among different strains (P<0.05). The same as below. |
2.3 耐低糖乳酸菌的乳酸产量和乳酸产率
表2 耐低糖乳酸菌在不同葡萄糖浓度培养基中培养48 h的乳酸产量Table 2 Lactic acid yield of low-sugar-tolerant lactic acid bacteria cultured in media with different glucose concentrations for 48 hg/L |
| 菌株 Strains | 葡萄糖浓度 Glucose concentrations/(g/L) | ||||
|---|---|---|---|---|---|
| 20 | 2 | 0.2 | 0.02 | 0.002 | |
| A1 | 6.16±0.20d | 1.84±0.03b | 0.14±0.01b | 0.014±0.003 | 0.001 6±0.000 0 |
| A2 | 10.68±0.87b | 1.90±0.02ab | 0.14±0.01b | 0.018±0.001 | 0.001 8±0.000 0 |
| A5 | 12.14±0.65a | 1.93±0.01ab | 0.15±0.01b | 0.016±0.004 | 0.001 4±0.000 2 |
| A6 | 6.21±0.24d | 1.65±0.07c | 0.15±0.01b | 0.019±0.004 | 0.001 7±0.000 1 |
| A7 | 10.43±0.43b | 1.11±0.08d | 0.15±0.01b | 0.017±0.001 | 0.001 2±0.000 1 |
| A9 | 4.17±0.67e | 1.67±0.03c | 0.11±0.02c | 0.015±0.001 | 0.001 9±0.000 0 |
| B1 | 9.88±0.68b | 1.62±0.04c | 0.11±0.01c | 0.016±0.008 | 0.001 5±0.001 1 |
| B2 | 11.82±1.07a | 1.90±0.00ab | 0.18±0.02a | 0.017±0.001 | 0.001 5±0.000 3 |
| B4 | 8.65±0.31c | 1.71±0.07c | 0.11±0.01c | 0.016±0.002 | 0.001 6±0.000 2 |
| C1 | 10.27±0.75b | 1.96±0.03a | 0.15±0.02b | 0.014±0.001 | 0.001 3±0.000 3 |
表3 耐低糖乳酸菌在不同葡萄浓度培养基中培养48 h的乳酸产率Table 3 Lactic acid productivity of low-sugar-tolerant lactic acid bacteria cultured in media with different glucose concentrations for 48 h |
| 菌株 Strains | 葡萄糖浓度 Glucose concentrations/(g/L) | ||||
|---|---|---|---|---|---|
| 20 | 2 | 0.2 | 0.02 | 0.002 | |
| A1 | 0.77±0.02de | 0.96±0.03ab | 0.81±0.03cd | 0.80±0.09abc | 0.85±0.07ab |
| A2 | 0.82±0.05cde | 0.97±0.01ab | 0.85±0.07c | 0.89±0.07ab | 0.94±0.02a |
| A5 | 0.97±0.01a | 0.97±0.02ab | 0.86±0.04bc | 0.66±0.13c | 0.93±0.07a |
| A6 | 0.65±0.04f | 0.96±0.03ab | 0.87±0.05bc | 0.74±0.15bc | 0.89±0.05ab |
| A7 | 0.98±0.01a | 0.88±0.07c | 0.96±0.03ab | 0.94±0.05a | 0.96±0.04a |
| A9 | 0.66±0.11f | 0.95±0.16ab | 0.73±0.10de | 0.92±0.09a | 0.95±0.04a |
| B1 | 0.84±0.01cd | 0.92±0.02bc | 0.70±0.05ef | 0.74±0.04bc | 0.72±0.28b |
| B2 | 0.88±0.06bc | 0.96±0.00a | 0.97±0.02a | 0.89±0.03ab | 0.90±0.07ab |
| B4 | 0.76±0.01e | 0.95±0.03ab | 0.63±0.06f | 0.90±0.05ab | 0.93±0.01a |
| C1 | 0.95±0.02ab | 0.99±0.02a | 0.81±0.08cd | 0.86±0.03ab | 0.95±0.02a |
2.4 耐低糖乳酸菌对苜蓿汁液的发酵效果
表4 耐低糖乳酸菌发酵24 h的苜蓿汁液pHTable 4 pH of alfalfa juice fermented by low-sugar-tolerant lactic acid bacteria for 24 h |
| 菌株 Strains | 可溶性糖浓度 Soluble sugar concentrations/(g/L) | |||
|---|---|---|---|---|
| 2 | 0.2 | 0.02 | 0.002 | |
| A1 | 4.52±0.04bc | 6.09±0.05a | 6.11±0.05b | 6.41±0.05c |
| A2 | 4.40±0.06de | 5.65±0.03d | 5.84±0.10c | 6.05±0.08f |
| A5 | 4.36±0.05e | 5.73±0.04cd | 6.21±0.04b | 6.39±0.03c |
| A6 | 4.50±0.02bc | 5.84±0.17bc | 6.68±0.05a | 6.76±0.06a |
| A7 | 4.22±0.04f | 5.86±0.04bc | 6.12±0.07b | 6.19±0.08e |
| A9 | 4.46±0.05cd | 5.79±0.02bcd | 6.16±0.06b | 6.45±0.06bc |
| B1 | 4.61±0.04a | 5.91±0.17b | 6.68±0.06a | 6.71±0.07a |
| B2 | 4.46±0.09cd | 5.67±0.06d | 5.88±0.06c | 6.28±0.03d |
| B4 | 4.57±0.05ab | 5.77±0.01bcd | 6.06±0.18b | 6.53±0.01b |
| C1 | 4.31±0.04e | 5.49±0.04e | 5.83±0.09c | 6.08±0.03f |
2.5 ARTP诱变致死率
2.6 突变菌株的初筛
表5 突变菌株HC值Table 5 HC value of mutant strains |
| 菌株 Strains | HC值 HC value | 菌株 Strains | HC值 HC value | |
|---|---|---|---|---|
| A2 | 1.21±0.09fg | YB21 | 1.34±0.11cdefg | |
| A5 | 1.24±0.03defg | YB22 | 1.33±0.10defg | |
| A7 | 1.21±0.14fg | YB23 | 1.32±0.15defg | |
| B2 | 1.18±0.06g | YB24 | 1.32±0.25defg | |
| C1 | 1.22±0.09efg | YB25 | 1.34±0.11cdefg | |
| YA21 | 1.30±0.14defg | YB26 | 1.25±0.13defg | |
| YA22 | 1.41±0.22cdefg | YB27 | 1.44±0.08cdefg | |
| YA23 | 1.28±0.08defg | YB28 | 1.50±0.31cdefg | |
| YA24 | 1.66±0.31bc | YB29 | 1.51±0.28cdefg | |
| YA51 | 1.92±0.20b | YC11 | 1.83±0.26b | |
| YA52 | 1.43±0.04cdefg | YC12 | 1.36±0.08cdefg | |
| YA53 | 1.41±0.12cdefg | YC13 | 1.34±0.16cdefg | |
| YA54 | 1.54±0.08cde | YC14 | 1.21±0.07fg | |
| YA55 | 1.34±0.10cdefg | YC15 | 1.36±0.07cdefg | |
| YA56 | 2.28±0.24a | YC16 | 1.42±0.12cdefg | |
| YA57 | 1.26±0.09defg | YC17 | 1.52±0.12cdef | |
| YA71 | 1.47±0.17cdefg | |||
| YA72 | 1.40±0.16cdefg | |||
| YA73 | 1.55±0.19cd |
2.7 突变菌株的复筛
2.7.1 突变菌株的产酸能力
表6 突变菌株在不同葡萄糖浓度培养基中培养48 h的pHTable 6 pH of mutant strains cultured in media with different glucose concentrations for 48 h |
| 菌株 Strains | 葡萄糖浓度 Glucose concentrations/(g/L) | ||||
|---|---|---|---|---|---|
| 20 | 2 | 0.2 | 0.02 | 0.002 | |
| A2 | 3.68±0.02cde | 5.11±0.02ef | 5.83±0.04ef | 6.05±0.01e | 6.01±0.04f |
| A5 | 3.84±0.04b | 5.34±0.07d | 6.38±0.03b | 6.48±0.11b | 6.53±0.03b |
| A7 | 3.64±0.01def | 5.12±0.01ef | 5.86±0.05e | 6.08±0.04e | 6.19±0.01d |
| B2 | 3.94±0.10a | 5.56±0.01a | 6.52±0.01a | 6.65±0.02a | 6.66±0.01a |
| C1 | 3.70±0.03cde | 5.34±0.14d | 5.80±0.10efg | 5.88±0.04fgh | 5.91±0.03ghi |
| YA24 | 3.61±0.03ef | 5.09±0.06f | 5.49±0.02i | 5.81±0.07gh | 5.87±0.02hi |
| YA51 | 3.63±0.04def | 5.06±0.06f | 5.68±0.03h | 5.85±0.03gh | 5.99±0.09fg |
| YA54 | 3.68±0.08cde | 5.52±0.02ab | 6.21±0.03c | 6.34±0.06c | 6.31±0.04c |
| YA56 | 3.56±0.04f | 5.08±0.03f | 5.49±0.04i | 5.68±0.03i | 5.83±0.07i |
| YA71 | 3.71±0.04cd | 5.50±0.03ab | 6.08±0.04d | 6.21±0.07d | 6.36±0.07c |
| YA73 | 3.72±0.05cd | 5.36±0.04cd | 5.76±0.10fgh | 5.79±0.03h | 5.97±0.06fg |
| YB28 | 3.73±0.05c | 5.57±0.05a | 5.78±0.03eg | 5.96±0.10f | 6.03±0.04ef |
| YB29 | 3.82±0.06b | 5.45±0.05b | 6.14±0.05cd | 6.38±0.04c | 6.52±0.05b |
| YC11 | 3.68±0.02cde | 5.44±0.07bc | 5.72±0.08gh | 5.89±0.03fg | 5.92±0.05gh |
| YC17 | 3.70±0.02cde | 5.19±0.04e | 5.71±0.05gh | 6.09±0.05e | 6.11±0.04e |
2.7.2 突变菌株的乳酸产量及乳酸产率
表7 突变菌株在不同葡萄糖浓度培养基中培养48 h的乳酸产量Table 7 Lactic acid yield of mutant strains cultured in media with different glucose concentrations for 48 hg/L |
| 菌株 Strains | 葡萄糖浓度 Glucose concentrations/(g/L) | ||||
|---|---|---|---|---|---|
| 20 | 2 | 0.2 | 0.02 | 0.002 | |
| A2 | 10.68±0.87def | 1.90±0.02ab | 0.14±0.01e | 0.018±0.001ab | 0.001 8±0.000 0abcd |
| A5 | 12.14±0.65bcd | 1.93±0.01a | 0.15±0.01bcde | 0.016±0.004abcd | 0.001 4±0.000 2cde |
| A7 | 10.43±0.43ef | 1.11±0.08f | 0.15±0.01de | 0.017±0.001abc | 0.001 2±0.000 1e |
| B2 | 11.82±1.07bcdef | 1.90±0.00ab | 0.18±0.02a | 0.017±0.001abc | 0.001 5±0.000 3bcde |
| C1 | 10.27±0.75f | 1.96±0.03a | 0.15±0.02cde | 0.014±0.001d | 0.001 3±0.000 3de |
| YA24 | 12.29±1.24bc | 1.62±0.05de | 0.16±0.01abcd | 0.018±0.001a | 0.002 0±0.000 2ab |
| YA51 | 12.75±0.72abc | 1.78±0.06bc | 0.17±0.00a | 0.018±0.000a | 0.001 5±0.000 2bcde |
| YA54 | 12.32±0.15bc | 1.69±0.06cd | 0.17±0.00ab | 0.017±0.000abc | 0.001 9±0.000 2abc |
| YA56 | 14.16±1.35a | 1.89±0.02ab | 0.18±0.01a | 0.018±0.001a | 0.001 9±0.000 1abc |
| YA71 | 11.39±0.87cef | 1.73±0.08cd | 0.17±0.01ab | 0.015±0.000bcd | 0.001 2±0.000 2e |
| YA73 | 11.93±0.52bce | 1.79±0.18bc | 0.17±0.01abcd | 0.018±0.000a | 0.001 9±0.000 2abc |
| YB28 | 12.76±0.58abc | 1.61±0.09de | 0.17±0.01a | 0.017±0.000abc | 0.002 0±0.000 2a |
| YB29 | 13.00±0.21abc | 1.53±0.06e | 0.17±0.01abc | 0.015±0.001cd | 0.001 4±0.000 1cde |
| YC11 | 13.16±0.98ab | 1.70±0.06cd | 0.16±0.00abcd | 0.016±0.001abc | 0.001 7±0.000 2abcd |
| YC17 | 12.69±1.15abc | 1.73±0.05cd | 0.17±0.01ab | 0.017±0.001abc | 0.001 8±0.000 3abc |
表8 突变菌株在不同葡萄糖浓度培养基中培养48 h的乳酸产率Table 8 Lactic acid productivity of mutant strains cultured in media with different glucose concentrations for 48 h |
| 菌株 Strains | 葡萄糖浓度 Glucose concentrations/(g/L) | ||||
|---|---|---|---|---|---|
| 20 | 2 | 0.2 | 0.02 | 0.002 | |
| A2 | 0.82±0.05d | 0.97±0.01ab | 0.85±0.07cd | 0.89±0.07ab | 0.94±0.02 |
| A5 | 0.97±0.01ab | 0.97±0.02ab | 0.86±0.04cd | 0.66±0.13c | 0.93±0.07 |
| A7 | 0.98±0.01ab | 0.88±0.07ef | 0.96±0.03ab | 0.94±0.05ab | 0.96±0.04 |
| B2 | 0.88±0.06cd | 0.96±0.00abc | 0.97±0.02a | 0.89±0.03ab | 0.90±0.07 |
| C1 | 0.95±0.02abc | 0.99±0.02a | 0.81±0.08d | 0.86±0.03b | 0.95±0.02 |
| YA24 | 0.91±0.09abc | 0.89±0.05cdef | 0.88±0.05bcd | 0.91±0.07ab | 0.91±0.05 |
| YA51 | 0.94±0.01abc | 0.94±0.00abcde | 0.96±0.03a | 0.97±0.04a | 0.96±0.03 |
| YA54 | 0.93±0.01abc | 0.91±0.04bcde | 0.95±0.02ab | 0.95±0.03ab | 0.92±0.12 |
| YA56 | 0.96±0.04abc | 0.98±0.01ab | 0.95±0.02ab | 0.97±0.01a | 0.93±0.02 |
| YA71 | 0.93±0.05abc | 0.95±0.01abcd | 0.93±0.03abc | 0.91±0.05ab | 0.89±0.06 |
| YA73 | 0.91±0.00abc | 0.94±0.07abcde | 0.95±0.04ab | 0.93±0.05ab | 0.93±0.03 |
| YB28 | 0.93±0.06abc | 0.89±0.05def | 0.96±0.04ab | 0.91±0.04ab | 0.93±0.03 |
| YB29 | 0.99±0.01a | 0.84±0.04f | 0.92±0.06abc | 0.89±0.03ab | 0.94±0.03 |
| YC11 | 0.94±0.05abc | 0.95±0.01abcde | 0.92±0.02abc | 0.93±0.02ab | 0.96±0.02 |
| YC17 | 0.90±0.03bc | 0.93±0.05abcde | 0.90±0.02abc | 0.93±0.03ab | 0.93±0.02 |
2.8 突变菌株的分子生物学鉴定
图4 突变菌株YA56的系统发育树Lactiplantibacillus plantarum strain CAU6347:植物乳杆菌CAU6347菌株;Levilactobacillus fajinensis strain 218-6:法金发酵乳杆菌218-6菌株;Secundilactobacillus odoratifolii strain JCM 15043:香叶次生乳杆菌JCM15043菌株;Secundilactobacillus paracolliculoides strain JCM 11969:副拟盘状次生乳杆菌JCM 11969 菌株;Pancilactobacillus vaccinostercus strain NRIC 1075:牛粪乳杆菌NRIC 1075菌株;Liquorilactobacillus satsumensis strain NRIC 0604:萨摩液体乳杆菌NRIC 0604菌株;Companilactobacillus metriopterae strain Hime5-1:伴生乳杆菌Hime5-1菌株。 Fig.4 Phylogenetic tree of mutant strain YA56 |
2.9 突变菌株的遗传稳定性
2.10 突变菌株对苜蓿汁液的发酵效果
表9 初始菌株和突变菌株发酵24 h的苜蓿汁液pHTable 9 pH of alfalfa juice fermented by original strain and mutant strains for 24 h |
| 菌株 Strains | 可溶性糖浓度 Soluble sugar concentrations/(g/L) | |||
|---|---|---|---|---|
| 2 | 0.2 | 0.02 | 0.002 | |
| A2 | 4.40±0.06ab | 5.65±0.03bc | 5.84±0.10cde | 6.05±0.08ef |
| A5 | 4.36±0.05bc | 5.73±0.04b | 6.21±0.04a | 6.39±0.03a |
| A7 | 4.22±0.04d | 5.86±0.04a | 6.12±0.07b | 6.19±0.08c |
| B2 | 4.46±0.09a | 5.67±0.06bc | 5.88±0.06c | 6.28±0.03b |
| C1 | 4.31±0.04c | 5.49±0.04e | 5.83±0.09cde | 6.08±0.03def |
| YA24 | 4.10±0.02fg | 5.65±0.03bc | 5.86±0.04cd | 6.16±0.05cd |
| YA51 | 4.10±0.02fg | 5.54±0.05de | 5.88±0.04c | 6.02±0.04f |
| YA54 | 4.13±0.01efg | 5.52±0.05de | 5.81±0.03cde | 6.13±0.05cde |
| YA56 | 4.06±0.03g | 5.49±0.03e | 5.68±0.03g | 6.01±0.04f |
| YA71 | 4.16±0.05def | 5.47±0.07e | 5.74±0.05efg | 6.05±0.05ef |
| YA73 | 4.19±0.02de | 5.67±0.10bc | 5.90±0.04c | 6.20±0.04c |
| YB28 | 4.06±0.01g | 5.64±0.05bc | 5.78±0.03def | 6.07±0.02def |
| YB29 | 4.13±0.05efg | 5.37±0.03f | 5.70±0.03fg | 6.08±0.04def |
| YC11 | 4.18±0.03def | 5.68±0.04bc | 5.90±0.03c | 6.19±0.08c |
| YC17 | 4.19±0.05de | 5.59±0.05cd | 5.83±0.05cde | 6.08±0.04def |

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