Variations of Soybean Meal and Corn Mixed Substrates in Physicochemical Characteristics and Microbiota During Two-Stage Solid-State Fermentation.

Weifa Su,Zipeng Jiang,Lihong Hao,Tao Gong,Yizhen Wang,Yu Zhang,Shuai Du,Cheng Wang,Zeqing Lu,Wentao Li,Mingliang Jin

doi:10.3389/fmicb.2021.688839

Abstract

Corn germ meal (CGM) and corn gluten feed (CGF) are the two main corn byproducts (CBs) obtained from corn starch extraction. Due to their high fiber content, low protein content, and severe imbalance of amino acid, CBs are unable to be fully utilized by animals. In this study, the effect of microorganism, proteases, temperature, solid–liquid ratio, and time on nutritional properties of CB mixture feed (CMF) was investigated with the single-factor method and the response surface method to improve the nutritional quality and utilization of CBs. Fermentation with Pichia kudriavzevii, Lactobacillus plantarum, and neutral protease notably improved the nutritional properties of CMF under the fermentation conditions of 37°C, solid–liquid ratio (1.2:1 g/ml), and 72 h. After two-stage solid-stage fermentation, the crude protein (CP) and trichloroacetic acid-soluble protein (TCA-SP) in fermented CMF (FCMF) were increased (p < 0.05) by 14.28% and 25.53%, respectively. The in vitro digestibility of CP and total amino acids of FCMF were significantly improved to 78.53% and 74.94%, respectively. In addition, fermentation degraded fiber and provided more organic acids in the CMF. Multiple physicochemical analyses combined with high-throughput sequencing were performed to reveal the dynamic changes that occur during a two-stage solid-state fermentation process. Generally, Ascomycota became the predominant members of the community of the first-stage of fermentation, and after 36 h of anaerobic fermentation, Paenibacillus spp., Pantoea spp., and Lactobacillales were predominant. All of these processes increased the bacterial abundance and lactic acid content (p < 0.00). Our results suggest that two-stage solid-state fermentation with Pichia kudriavzevii, Lactobacillus plantarum, and protease can efficiently improve protein quality and nutrient utilization of CMF.

Highlights

The competition for food between humans and livestock has become a topic with great concern in the past few years
Based on the results of the single-factor experiment (Table 1), corn byproducts mixture feed (CMF) fermented with P. kudriavzevii PKWF, L. plantarum CWLP, and neutral protease (CMFPLN) has the highest content of crude protein (CP), trichloroacetic acid soluble protein (TCA-SP), and ether extract (EE) compared with the other fermentation combinations, which were 9.5%, 22.1%, and 38.1% higher than that of CMF, respectively
crude fiber (CF) of CMFPLN is significantly lower than that of CMF (p < 0.05). These results indicate that the process of fermentation with P. kudriavzevii PKWF, L. plantarum CWLP, and neutral protease significantly improved the nutritional composition of CMF

Summary

Introduction

The competition for food between humans and livestock has become a topic with great concern in the past few years. Pichia kudriavzevii, and Lactobacillus plantarum were widely used SSF strains (Ni et al, 2017). Bacillus subtilis can degrade large molecular proteins to produce small peptides in SSF due to their capacity to secrete extracellular protease (Soares et al, 2005). Our previous research shows that solid fermented soybean meal–corn mixture feed and distilled dried grain with soluble Bacillus subtilis and Lactobacillus plantarum can effectively improve their nutritional value and increase the content of small peptides and lactic acid (Shi et al, 2017; Wang et al, 2018b; Zhang et al, 2018; Zong et al, 2020). We hypothesized that using protease instead of extracellular protease-producing Bacillus subtilis to ferment with Lactobacillus plantarum and Pichia kudriavzevii would have a better fermentation effect

Methods

Results

Discussion

Conclusion