Construction and Optimization of Corncob Fermentation Process Using Composite Microbial Inoculum

doi:10.13560/j.cnki.biotech.bull.1985.2025-1369

Abstract

Abstract:

Objective High-lignin straw exhibits low feed utilization efficiency due to its high content of acid detergent lignin (ADL). We developed a composite fermentation process using white-rot fungus, Bacillus subtilis, and Pichia pastoris, and evaluated its synergistic degradation effect in corncob. Method We constructed a three-strain composite fermentation system consisting of white-rot fungus BF-1 (isolated from Lentinula edodes) as the core functional strain, together with Bacillus subtilis and Pichia pastoris at a cell mass ratio of 1∶1∶1. Corncob served as the fermentation substrate, and single-strain fermentation of BF-1 was used as the control. The degradation efficiency of ADL was compared using single-factor experiments (temperature: 28–32 ℃, moisture content: 40%–50%, inoculum size: 1%–5%). Response surface methodology was then employed to optimize the fermentation conditions for the three-strain system. Morphological changes in corncobs were examined by scanning electron microscopy (SEM). Crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF) were measured to evaluate the relative feed value (RFV) and relative feed quality (RFQ). Result Single-factor experiments showed that both fermentation systems achieved optimal ADL degradation at 30 ℃, 45% moisture content, and 3% inoculum size. Under these conditions, the ADL degradation rate of single-strain fermentation was 42.29%, while that of the three-strain fermentation was 58.83%. The degradation efficiency of the three-strain system was significantly higher than that of the single-strain system (P<0.01). Response surface methodology identified the optimal conditions for three-strain fermentation as 29.8 ℃, 45.2% moisture, and 3.1% inoculum, achieving an ADL degradation rate of 63.42%. During fermentation, the activities of laccase (Lac), manganese peroxidase (MnP), and lignin peroxidase (LiP) increased continuously over time. Scanning electron microscopy revealed that after three-strain fermentation, the surface structure of the corncob was more significantly disrupted, exhibiting a loose and porous morphology. After 21 days of fermentation, the CP content in the three-strain system increased by 1.43% (P<0.01), while NDF and ADF contents decreased significantly (P<0.01), with degradation rates of 22.12% and 33.97%, respectively. RFQ and RFV increased by 82.80% and 17.21%, respectively. Conclusion The three-strain synergistic fermentation effectively degraded corncob lignin, achieving an ADL degradation rate of 63.42%, a 1.43% increase in CP content, and significant fiber degradation. RFQ was increased by 82.80%, and RFV was substantially enhanced. These findings provide a technical support for the utilization of corncobs as animal feed.

Key words: white-rot fungi, corncob, acid detergent lignin, nutritional quality, feeding value

CHEN Wen-yan, ZHOU Rui, WU Hui-hao, LI Yao-dong, YANG Jie, ZANG Rong-xin, XU Hong-wei. Construction and Optimization of Corncob Fermentation Process Using Composite Microbial Inoculum[J]. Biotechnology Bulletin, 2026, 42(10): 37-46.

Figures/Tables 9

References 35

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因素 Factor	水平 Level	对照组 Control group	单菌处理组 Single-bacteria treatment group		三菌处理组 Three-bacteria treatment group		P-value
因素 Factor	水平 Level	ADL含量	ADL含量	ADL降解率	ADL含量	ADL降解率	P-value
温度	28 ℃	5.77±0.41A	4.9±0.22B	15.02±3.86b	4.65±0.1B	19.35±1.8a	<0.01
	30 ℃	5.77±0.41A	3.33±0.11B	42.29±1.93b	2.69±0.1B	53.4±1.72a	<0.01
	32 ℃	5.77±0.41A	5.14±0.09B	10.98±1.57b	4.31±0.1B	25.31±1.69a	<0.01
含水量	40%	5.77±0.41A	5.34±0.12BC	7.45±2b	3.74±0.6B	32.29±1.15a	<0.01
	45%	5.77±0.41A	4.42±0.2B	23.34±3.49b	2.38±0.07B	58.83±1.24a	<0.01
	50%	5.77±0.41A	5.27±0.14B	8.61±2.47b	4.14±0.67B	36.24±1.78a	<0.01
接种量	1%	5.77±0.41A	5.16±0.17B	10.63±2.86b	4.7±0.17B	18.48±2.91a	<0.01
	3%	5.77±0.41A	3.36±0.16B	41.83±2.8b	2.57±0.09C	55.42±1.54a	<0.01
	5%	5.77±0.41A	4.46±0.23B	22.76±3.95b	3.88±0.07C	32.78±1.27a	<0.01

因素 Factor	水平 Level	对照组 Control group	单菌处理组 Single-bacteria treatment group		三菌处理组 Three-bacteria treatment group		P-value
因素 Factor	水平 Level	ADL含量	ADL含量	ADL降解率	ADL含量	ADL降解率	P-value
温度	28 ℃	5.77±0.41A	4.9±0.22B	15.02±3.86b	4.65±0.1B	19.35±1.8a	<0.01
	30 ℃	5.77±0.41A	3.33±0.11B	42.29±1.93b	2.69±0.1B	53.4±1.72a	<0.01
	32 ℃	5.77±0.41A	5.14±0.09B	10.98±1.57b	4.31±0.1B	25.31±1.69a	<0.01
含水量	40%	5.77±0.41A	5.34±0.12BC	7.45±2b	3.74±0.6B	32.29±1.15a	<0.01
	45%	5.77±0.41A	4.42±0.2B	23.34±3.49b	2.38±0.07B	58.83±1.24a	<0.01
	50%	5.77±0.41A	5.27±0.14B	8.61±2.47b	4.14±0.67B	36.24±1.78a	<0.01
接种量	1%	5.77±0.41A	5.16±0.17B	10.63±2.86b	4.7±0.17B	18.48±2.91a	<0.01
	3%	5.77±0.41A	3.36±0.16B	41.83±2.8b	2.57±0.09C	55.42±1.54a	<0.01
	5%	5.77±0.41A	4.46±0.23B	22.76±3.95b	3.88±0.07C	32.78±1.27a	<0.01

方差来源 Variance source	平方和 Sum of squares	自由度 Degree of freedom	均方差 Mean square	F值 F value	P-value	显著性 Significance
模型Model	4 614.81	9	512.76	49.08	<0.000 1	**
A-温度	124.81	1	124.81	11.95	0.010 6	*
B-含水量	90.19	1	90.19	8.63	0.021 8	*
C-接种量	155.13	1	155.13	14.85	0.006 3	**
AB	0.005 6	1	0.005 6	0.000 5	0.982 1
AC	8.01	1	8.01	0.767 0	0.410 2
BC	43.45	1	43.45	4.16	0.080 8
A²	1 073.31	1	1 073.31	102.73	<0.000 1	**
B²	141.00	1	141.00	13.50	0.007 9	**
C²	1 731.93	1	1 731.93	165.78	<0.000 1	**
残差	73.13	7	10.45
失拟项	12.09	3	4.03	0.264 2	0.848 5	no significance
纯误差	61.04	4	15.26
总变异	4 687.94	16
R²					0.984 4
R²_Adj					0.964 3
R²_Pre					0.938 4
Adeq precision					21.201 5
CV （%）					7.84

方差来源 Variance source	平方和 Sum of squares	自由度 Degree of freedom	均方差 Mean square	F值 F value	P-value	显著性 Significance
模型Model	4 614.81	9	512.76	49.08	<0.000 1	**
A-温度	124.81	1	124.81	11.95	0.010 6	*
B-含水量	90.19	1	90.19	8.63	0.021 8	*
C-接种量	155.13	1	155.13	14.85	0.006 3	**
AB	0.005 6	1	0.005 6	0.000 5	0.982 1
AC	8.01	1	8.01	0.767 0	0.410 2
BC	43.45	1	43.45	4.16	0.080 8
A²	1 073.31	1	1 073.31	102.73	<0.000 1	**
B²	141.00	1	141.00	13.50	0.007 9	**
C²	1 731.93	1	1 731.93	165.78	<0.000 1	**
残差	73.13	7	10.45
失拟项	12.09	3	4.03	0.264 2	0.848 5	no significance
纯误差	61.04	4	15.26
总变异	4 687.94	16
R²					0.984 4
R²_Adj					0.964 3
R²_Pre					0.938 4
Adeq precision					21.201 5
CV （%）					7.84

组别 Group	对照组 Control group	发酵时间 Fermentation time （d）			P-value
组别 Group	对照组 Control group	7	14	21	P-value
粗蛋白（CP）	2.8±1.14C	4.69±0.62B	5.95±0.29A	6.79±0.44A	<0.001
CP增长率		0.68±0.22C	1.13±0.1B	1.43±0.16A	<0.001
酸性洗涤纤维（ADF）	43.57±1.16A	38.19±0.4B	35.67±1.98C	28.77±1.08D	<0.001
ADF降解率		12.36±0.92C	18.13±4.55B	33.97±2.47A	<0.001
中性洗涤粗纤维（NDF）	78.31±1.37A	68.13±1.36B	66.56±0.51B	60.99±1.83C	<0.001
NDF降解率		13.01±1.73C	15.01±0.65B	22.12±2.33A	<0.001
相对饲用品质（RFQ）	56.22±2.7D	74.55±0.76C	81.07±4.06B	102.77±3.5A	<0.001
相对饲用价值（RFV）	41.07±0.73B	40.7±1.44B	42.79±2.38B	48.14±2.04A	<0.001