DDC Tech Day | Microbial Fermented Feed and Its Applications

Abstract: This article reviews the use of fermentation engineering to produce microbial feed from fermented oilseed meals, straw, and fruit residues, which enhances feed utilization, improves feed quality, and mitigates environmental pollution. It also highlights how this approach helps alleviate China's shortage of protein feed ingredients. Additionally, the paper discusses the application of microbially fermented feed in animal production and identifies both the challenges currently faced by fermented feed products and their promising future prospects.

Keywords: Fermentation Engineering; Oilseed Meal Raw Materials; Fruit Residue; Microbial Fermentation Feed

Fermentation engineering, also known as microbial engineering, refers to a technology that leverages modern engineering techniques to harness specific functions of microorganisms, enabling the production of useful products for humanity—or directly applying microorganisms in industrial manufacturing processes. ^[1] The core of fermentation engineering lies in microorganisms, especially those that have been DNA Reengineered microorganisms. Currently, fermentation technology has yielded excellent results when applied to feed production and animal husbandry. In recent years, the continuous rise in feed原料 prices has significantly increased livestock and poultry farming costs, severely impacting the development of China's animal husbandry sector and feed industry. Therefore, enhancing feed utilization efficiency and improving feed quality have become key research priorities for the current feed industry. ^[2] This article primarily outlines the application of fermentation engineering in feed ingredients.

1   Microbial fermentation ^[3]

To eliminate anti-nutritional factors, accumulate beneficial metabolic products, and enhance feed utilization as well as animals' digestive capacity, the key approaches include: 1. Degradation of anti-nutritional components in protein-rich feeds such as soybean meal, cottonseed meal, rapeseed meal, and peanut meal—specifically targeting allergenic proteins in soybean meal, gossypol in cottonseed meal, and glucosinolates in rapeseed meal—while also conducting *in vitro* protein digestion. Fermentation can effectively modify the physicochemical properties of these raw materials, reducing anti-nutritional factors while generating valuable compounds that promote animal growth, improve feed digestibility, and boost palatability. Additionally, fermentation helps extend storage life and even detoxify harmful substances, transforming toxic or mildly toxic feed ingredients into safe, high-quality options. This process not only enhances nitrogen utilization but also minimizes nitrogen-related pollution in livestock manure, thereby mitigating environmental impact. 2. Fermentation of non-starch polysaccharides in feed ingredients like barley and crop residues, making these components more readily digestible and absorbable by animals, thus boosting feed metabolism and palatability. ^[4] 。

2   Fermented feed ingredients

2.1  Fermented粕-based ingredients

Soybean meal is a byproduct of soybean oil extraction, rich in protein and boasting a high amino acid content—it’s a commonly used plant-based protein ingredient in animal feed. Ma Wenqiang and others ^[5] After fermenting soybean meal with Bacillus subtilis, Saccharomyces cerevisiae, and lactic acid bacteria, the crude protein content was increased. 13.48% , crude fat content increased 18.18% The phosphorus content has increased. 55.56% , amino acids were enhanced 11.49% , trypsin inhibitors and other antinutritional factors have been thoroughly eliminated. Mo Zhongwen et al. ^[6] Fermenting soybean meal using a mixed strain of Aspergillus oryzae and brewer's yeast increased the crude protein content. 12.1% ; Yang Xu ^[7] Once using brewer's yeast to perform solid-state fermentation on soybean meal, the protein content was increased. 9.55% 。

Cottonseed meal boasts a high amino acid content and a crude protein level second only to soybean meal, making it a premium plant-based protein feed. However, the free gossypol contained within can pose significant toxicity to animals, thereby limiting its use in animal feed. In recent years, fermenting cottonseed meal has proven effective in reducing free gossypol levels, enhancing protein digestibility, and improving overall meal quality—qualities that promise broad application potential. Zhu Ge Bin and colleagues ^[8] Utilizing mixed-microbe fermentation of cottonseed meal to increase the small-peptide content to 18.36% , the in vitro digestibility increased to 88.59% , significantly improved cottonseed meal protein. Qiao Xiaoyan et al. ^[9] After fermenting cottonseed meal with Candida tropicalis and Lactobacillus casei, the detoxification rate of gossypol reached 48.1% , the levels of small peptides have increased 10.97% , amino acids were enhanced 10.81% , Phytic acid reduced 1.54% ; Nie Pengbo ^[10] Using Bacillus cereus fermentation to enhance the protein content of cottonseed meal. 3.79% , Free Gossypol Detoxification Rate 53.4% ; Jin Hongchun ^[11] Fermenting cottonseed meal with composite Bacillus strains achieves a free gossypol removal rate of 96.52% 。

Rapeseed meal contains anti-nutritional factors such as glucosinolates, erucic acid, tannins, phytic acid, and sinigrin, which severely limit its use in animal feed. Therefore, detoxification of rapeseed meal through fermentation has already gained relatively widespread nutritional benefits. Wang Gang ^[12] By blending solid-state fermented rapeseed meal, the glucosinolate degradation rate is achieved as 53.4% , crude protein levels have increased 5.58% , rapeseed peptides enhanced 8.1% , the in vitro digestibility of the protein has improved. 1.94% ; Lu Yu and others ^[13] Through solid-state mixed-microbial fermentation, the glucosinolate removal rate reaches 97% ; Sun Lin et al. ^[14] Solid-state fermentation using Lactobacillus, Bacillus subtilis, Bacillus cereus, and Clostridium butyricum achieves a significant reduction in glucosinolates in rapeseed meal. 85.19% , crude protein content increases 4.37% 。

Our country is a major agricultural nation with abundant crop straw resources—straw contains approximately 65%-80% The dry matter can provide energy for animals, yet currently there is an insufficient supply used for feed. 10% , the vast majority of straw is either directly returned to the fields or used as fuel, leading to significant resource waste and further polluting the environment. ^[15] Therefore, using fermentation to process straw into animal feed holds significant practical value. Huang Qian and others ^[16] Using mixed microbial fermentation to break down straw, the lignin degradation rate reaches 44.77% , the cellulose degradation rate reaches 41.48% Li Riqiang and others ^[17] Solid-state fermentation was used to increase the true protein content of corn stover. 129.6% , crude protein levels have increased 29.59% Wang Yiming ^[18] After mixed-microbial fermentation, straw cellulose is degraded into 38.5% , degradation rate is 28.2% ; Hemicellulose is degraded into 13.7% , degradation rate is 27.5% ; Protein content increased to 15.43% , an increase compared to before fermentation 12.32% 。

2.2  Fruit pulp

As a major agricultural country, China generates vast amounts of agricultural by-products annually, such as straw and fruit pulp. The challenge lies in how to efficiently and scientifically convert these waste materials into valuable feed ingredients. By employing fermentation techniques to process these by-products into protein-rich feed, we can not only enhance resource utilization but also mitigate environmental pollution and improve ecological sustainability. Guangxi Jinmaike Biotechnology Co., Ltd. utilizes sugarcane and cassava residues as raw materials to produce single-cell protein feed ingredients. This innovative approach enables the development of diverse protein-based feed resources, reducing the feed industry's reliance on grain crops and ultimately boosting the growth of the livestock sector. ^[19] Bagasse is the primary byproduct of sugar mills, containing only 1.5% to 3.0% The crude protein content is low, resulting in poor nutritional value and palatability. To alleviate the supply-demand imbalance of feed grains in China, research was conducted on a raw-material fermentation process for bagasse-based feed. Hu Yongmei and others ^[20] The experimental results show that , Using three strains—Aspergillus niger, Trichoderma viride, and Candida utilis—we ferment bagasse and molasses in a ratio of 8:2 Ingredients, ingredient-to-water ratio 1:3 , Add 6% (NH ₄)₂ SO ₄ , Nature pH Value, Fermentation Temperature 30 ℃, Mixed-strain Fermentation 36h , the crude protein content of the fermented feed was increased to 11.48% The aroma and palatability have been significantly improved compared to bagasse, making it suitable as feed for cattle, sheep, and other livestock. Xu Yafei ^[21] Based on microbiology and fermentation engineering principles, this study employs microbial solid-state fermentation technology to explore the production of fermented feed using bagasse and sugarcane molasses, resulting in a high-value-for-feed product. Importantly, the process generates no "three wastes," thereby opening up a new pathway for the comprehensive utilization of bagasse and sugarcane molasses. This innovation holds significant implications for the sugarcane industry, livestock farming, the feed sector, and sustainable environmental development. Zhang Changxia ^[22] After mixed-microbe solid-state fermentation of apple pomace, the true protein content is 13.0 %, an increase compared to before fermentation 40 %, an improvement over the original fruit pulp 500 %. The activities of pectinase, protease, and cellulase were respectively 126.2U，2.9U，55.2U , and conducted a preliminary study on the enzymatic properties of pectinase. Oil tea seed wet residue is a byproduct remaining after oil extraction from oil tea seeds; if not fully utilized, discarding it not only wastes valuable resources but also pollutes the environment. Wang Xiaorong ^[23] The study investigated the feasibility of producing microbial biomass protein feed using oil tea seed wet residue as a raw material through solid-state fermentation, and conducted research and analysis on both the fermentation process and the resulting product. After fermentation, the dried product showed a crude protein content that significantly increased compared to the level before inoculation and fermentation. 22.54% Increase to 39.34% , the improvement rate is 74.53% , crude fiber consists of 46.18% Drop to 42.12% Degradation rate is 8.79% , which was detected 17 The content of all amino acids increased to varying degrees, with tyrosine showing the largest rise, followed by glutamic acid, leucine, alanine, and lysine.

3  Characteristics of microorganism-fermented feed and its role in animal husbandry

Microbial fermented feed boasts a natural fermentation aroma, excellent palatability, and strong appetite-stimulating effects. It contains a high concentration of beneficial bacteria, while the levels of harmful bacteria—such as E. coli, Salmonella, and Staphylococcus aureus (which are typical examples)—remain extremely low, not exceeding 10cfu/g ; The fermented finished product pH The value is relatively low, at 4.5 Right, it contains large amounts of organic acids (primarily lactic acid and acetic acid).

Microbial fermented feed can inhibit the proliferation of harmful bacteria, helping to maintain a healthy gut microbiota. By suppressing and preventing the growth of detrimental bacteria in the intestine, it promotes the increase of beneficial bacteria, thereby restoring and sustaining a balanced, health-promoting gut ecosystem. Primarily, 1 ）Inhibits pathogenic E. coli, Clostridium perfringens, Salmonella, β The proliferation of hemolytic bacteria and similar organisms. 2