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 husbandry and addresses the existing challenges as well as the promising future prospects for this innovative technology.

 

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

 

　　Fermentation engineering, also known as microbial engineering, refers to the use of modern engineering techniques to harness specific functions of microorganisms, enabling the production of valuable products for human benefit—or directly applying microorganisms in industrial manufacturing processes[1]. At the heart of fermentation engineering are microorganisms, particularly those that have been genetically engineered through DNA recombination. Currently, fermentation engineering has already demonstrated promising results in animal feed and livestock management. In recent years, rising prices of feed ingredients have significantly increased the costs of raising livestock and poultry, severely impacting the development of China's animal husbandry and feed industries. As a result, enhancing feed efficiency and improving feed quality have become key research priorities for the global feed industry today[2]. This article primarily provides an overview of how fermentation engineering is being applied to feed ingredients.

 

1. Microbial fermentation [3]

 

　　To eliminate anti-nutritional factors, accumulate beneficial metabolic products, and enhance feed utilization and animal digestive capacity, the main approaches include: degrading anti-nutritional components in protein-rich feeds such as soybean meal, cottonseed meal, rapeseed meal, and peanut meal—such as antigenic proteins in soybean meal, gossypol in cottonseed meal, and glucosinolates in rapeseed meal—while also conducting in vitro protein digestion. Fermentation can effectively alter the physicochemical properties of these meal-based raw materials, reducing anti-nutritional factors and generating valuable compounds that promote animal growth. This process not only boosts feed digestibility but also improves palatability, extends storage life, and even facilitates detoxification, transforming potentially toxic meals into safe, low-toxicity, high-quality feed ingredients. As a result, nitrogen utilization is enhanced, leading to reduced nitrogen pollution in livestock manure and minimizing environmental contamination from animal farming. Additionally, beneficial metabolic byproducts like small peptides and lactic acid are accumulated, helping to inhibit the proliferation of pathogenic microorganisms. Ultimately, this approach significantly cuts down—or even completely replaces—the need for antibiotics, while optimizing animal health and performance. For feed ingredients like barley and straw, non-starch polysaccharides can be digested in vitro, making them more readily accessible for animal digestion and absorption, thereby improving both feed metabolism and palatability [4].

 

2. Fermented Feed Ingredients

 

2.1 Fermented Bran-Based Raw Materials

 

　　Soybean meal is a byproduct of soybean oil extraction, rich in protein and boasting a high amino acid content. It is a commonly used plant-based protein ingredient in animal feed. According to Ma Wenqiang et al.[5], after fermenting soybean meal with Bacillus subtilis, Saccharomyces cerevisiae, and lactic acid bacteria, the crude protein content increased by 13.48%, crude fat rose by 18.18%, phosphorus levels climbed by 55.56%, and amino acids improved by 11.49%. Additionally, trypsin inhibitors and other antinutritional factors were completely eliminated. Meanwhile, Mo Zhongwen et al.[6] employed a mixed culture of Aspergillus oryzae and brewer’s yeast to ferment soybean meal, boosting the crude protein content by 12.1%. Similarly, Yang Xu[7] and colleagues utilized Saccharomyces cerevisiae for solid-state fermentation of soybean meal, resulting in a 9.55% increase in protein content.

 

　　Cottonseed meal boasts a high amino acid content and ranks second only to soybean meal in crude protein levels, making it a premium plant-based protein feed. However, the presence of free gossypol in cottonseed meal poses certain toxic risks to animals, thereby limiting its widespread use in animal feed. In recent years, fermentative treatment of cottonseed meal has emerged as an effective method to reduce free gossypol levels, enhance protein digestibility, and improve overall meal quality, opening up promising avenues for practical application. For instance, Zhu Ge Bin et al.[8] employed mixed-microbial fermentation to boost the small-peptide content in cottonseed meal to 18.36% and increase its in vitro digestibility to 88.59%, significantly enhancing the meal's protein value. Meanwhile, Qiao Xiao Yan et al.[9] utilized tropical Candida yeast and Lactobacillus casei to ferment cottonseed meal, achieving a gossypol detoxification rate of 48.1%, along with a 10.97% rise in small-peptide content and a 10.81% improvement in amino acid profile—while phytic acid levels were reduced by 1.54%. Additionally, Nie Peng Bo[10] applied Bacillus cereus fermentation to elevate cottonseed meal protein by 3.79% and achieve a free gossypol detoxification rate of 53.4%. More recently, Jin Hong Chun[11] employed a composite Bacillus strain to ferment cottonseed meal, successfully eliminating up to 96.52% of free gossypol.

 

　　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, fermentation-based detoxification of rapeseed meal has gained relatively widespread attention for improving its nutritional value. Wang Gang [12] achieved a 53.4% degradation rate of glucosinolates, along with a 5.58% increase in crude protein and an 8.1% rise in rapeseed peptides, while also enhancing the in vitro protein digestibility by 1.94% through mixed solid-state fermentation of rapeseed meal. Meanwhile, Lu Yu et al. [13] demonstrated that solid-state co-fermentation using multiple microbial strains could eliminate up to 97% of glucosinolates. Additionally, Sun Lin et al. [14] employed a solid-state fermentation process involving lactic acid bacteria, Bacillus subtilis, Bacillus cereus, and Clostridium butyricum, successfully reducing glucosinolate levels by 85.19% and boosting crude protein content by 4.37%.

 

　　China is a major agricultural country with abundant crop straw resources. Approximately 65% to 80% of the dry matter in straw can provide energy for animals, yet currently less than 10% of it is utilized as animal feed. The vast majority of straw is either directly returned to the fields or burned as fuel, leading to significant resource waste and further environmental pollution [15]. Therefore, employing fermentation methods to convert straw into animal feed holds immense practical significance. Huang Qian and colleagues [16] used mixed microbial fermentation to treat straw, achieving lignin degradation rates as high as 44.77% and cellulose degradation rates of 41.48%. Meanwhile, Li Riqiang and his team [17] enhanced the true protein content of corn straw by 129.6% and increased its crude protein level by 29.59% through solid-state fermentation. Wang Yiming [18], after conducting mixed-microbial fermentation, observed that straw cellulose was degraded by 38.5%, representing a degradation rate of 28.2%; hemicellulose was reduced by 13.7%, with a corresponding degradation rate of 27.5%. Additionally, the protein content in the fermented straw rose to 15.43%, an impressive 12.32% increase compared to the original material before fermentation.

 

2.2. Fruit Residue

 

　　As a major agricultural country, China generates vast amounts of agricultural by-products annually, such as straw and fruit residues. 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 animal feed, we can not only enhance resource utilization but also mitigate environmental pollution, thereby improving our ecological balance. Guangxi Jinmaike Biotechnology Co., Ltd. has pioneered the production of single-cell protein feed ingredients using sugarcane bagasse and cassava residue as raw materials. This innovative approach enables the development of diverse protein-based feed resources, reducing the feed industry's reliance on grain crops and fostering sustainable growth in the livestock sector [19]. Sugarcane bagasse, a primary by-product from sugar mills, contains only 1.5%–3.0% crude protein, making it nutritionally deficient and poorly palatable. To address the growing imbalance between feed grain supply and demand in China, researchers have conducted extensive studies on the fermentation process of raw sugarcane bagasse for feed production. Hu Yongmei and her team [20] demonstrated that by inoculating the substrate with a combination of *Aspergillus niger*, *Trichoderma viride*, and *Candida utilis*, along with a feed-to-water ratio of 8:2, a moisture level of 1:3, and supplementing with 6% (NH₄)₂SO₄ at natural pH, followed by incubation at 30°C for 36 hours, the crude protein content of the fermented feed could be significantly boosted to 11.48%. Moreover, the resulting product exhibited markedly improved aroma and palatability compared to raw bagasse, making it an ideal feed option for cattle, sheep, and other livestock. Building on microbiological and fermentation engineering principles, Xu Yafei [21] utilized microbial solid-state fermentation technology to explore the production of fermented feed from sugarcane bagasse and molasses. This method yields a high-quality feed ingredient with exceptional nutritional value, while eliminating harmful "three wastes" during the production process. As a result, this breakthrough opens up a new pathway for the comprehensive utilization of sugarcane bagasse and molasses, holding significant potential for advancing the sugarcane industry, livestock farming, and the broader feed sector—while also contributing to sustainable environmental development. Zhang Changxia [22] further advanced this research by conducting mixed-microbial solid-state fermentation on apple pomace, achieving a remarkable increase in true protein content—up to 13.0%, representing a 40% improvement over the unfermented material and a staggering 500% rise compared to the original pomace. Additionally, the study revealed notable enzymatic activities of pectinase (126.2 U), protease (2.9 U), and cellulase (55.2 U), laying the groundwork for a deeper understanding of pectinase properties. Meanwhile, oil tea seed wet residue—a by-product left after oil extraction from oil tea seeds—poses both resource-wasting and environmental challenges if improperly managed. Wang Xiaorong [23] investigated the feasibility of producing microbial biomass protein feed using oil tea seed wet residue through microbial solid-state fermentation. Her research meticulously examined the fermentation process and analyzed the resulting product. After fermentation and subsequent drying, the crude protein content of the feed surged dramatically—from 22.54% before inoculation to 39.34%, reflecting a substantial 74.53% increase. Meanwhile, crude fiber levels dropped from 46.18% to 42.12%, achieving a degradation rate of 8.79%. Importantly, the analysis also revealed that all 17 amino acids present in the feed showed varying degrees of enhancement post-fermentation, with tyrosine experiencing the most significant boost, followed closely by glutamic acid, leucine, alanine, and lysine.

 

3. Characteristics of Microbial 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 serve as typical examples)—remain extremely low, not exceeding 10 CFU/g. Additionally, the finished fermented product has a low pH, around 4.5, and is rich in 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. 1. It suppresses and prevents the emergence of harmful bacteria in the intestine, promoting the growth of beneficial bacteria and restoring a balanced gut ecosystem essential for health. Specifically, it targets pathogenic E. coli, Clostridium species, and Salmonella. β 1. The proliferation of hemolytic bacteria and other similar organisms. 2. Producing digestive enzymes and synthesizing vitamins—specifically, enzymes like amylase and protease, as well as B-complex vitamins; additionally, vitamin A synthesis has also been confirmed. 3. Enhancing immune function: By stimulating immune cells in the gut, these additives promote the production of local antibodies, thereby boosting macrophage activity. Notably, microbial feed additives containing vitamin A are known for their immune-boosting effects. 4. Generating hydrogen peroxide, which exerts a damaging effect on several potential pathogenic microorganisms. This compound is produced by certain specialized substances acting on specific substrates.

 

4. Application of Microbial Fermented Feed

 

　　Peng Zhongli [24] found that feeding microbial fermented feed to goats significantly improved their average daily weight gain in both Test Groups I and II compared to the control group (P < 0.01). Additionally, the apparent digestibility of crude protein, crude fiber, neutral detergent fiber, and acid detergent fiber was markedly enhanced (P < 0.05), while the incidence of disease was significantly reduced (P < 0.01). However, there were no significant differences in total protein, albumin, alanine aminotransferase, or aspartate aminotransferase levels among the groups (P > 0.05). Each goat in the test groups generated an additional income of 0.33 yuan and 0.15 yuan per day, respectively, compared to the control group. Lin Biaosheng [25] conducted a trial demonstrating that piglets weaned onto microbial fermented feed showed a 5.56% increase in average daily weight gain and a 3.53% reduction in feed-to-gain ratio compared to those fed conventional feed. Moreover, the experimental group exhibited a notable rise in beneficial gut bacteria and a decrease in fecal pH, with statistically significant differences from the control group (P < 0.05). Jin Zhuang [26] used lactic acid bacteria-fermented feed in a large-scale pig farm, revealing that pigs fed this type of feed experienced significantly higher feed intake, increased average daily weight gain, and improved feed conversion ratios, along with reduced disease incidence. Zhai Hengxiao [27] discovered that growing-finishing pigs fed fermented feed had a 5.02% higher average daily weight gain than those on conventional diets; however, there were no significant differences in daily weight gain, feed intake, or feed-to-gain ratio (P < 0.05). Economic analysis indicated that the fermented feed group yielded an average revenue increase of 17.09 yuan per pig compared to the standard compound feed group. Qiu Juan [28] reported that feeding fermented feed to piglets resulted in a 10.19% higher average daily weight gain compared to the control group, a difference that was statistically significant (P < 0.05). Although feed intake and feed-to-gain ratios did not show marked variations (P > 0.05), the fermented feed still demonstrated clear advantages. This suggests that incorporating bio-fermented feed into piglet diets can effectively enhance growth performance. Huang Shijin [29] found that, compared to the control group, feeding commercial tilapia supplemented with 10%, 15%, and 20% microbial fermented feed led to increases in daily weight gain of 1.75%, 22.14%, and 21.36%, respectively. Survival rates also improved significantly, reaching (96.10 ± 0.60)%, (98.07 ± 0.81)%, and (97.67 ± 0.63)%, respectively. Furthermore, feed conversion ratios decreased notably by 5.51%, 15.14%, and 15.60%, respectively, resulting in enhanced overall farming profitability, with the highest unit profit achieved when using 15% composite microbial fermented feed. Li Hui et al. [30] investigated the effects of fermenting soybean meal at varying replacement levels—25%, 50%, 75%, and 100%—for fishmeal in the basal diet on the growth and apparent digestibility of spotted catfish (Ictalurus punctatus). Their findings revealed that fermented soybean meal could fully replace fishmeal in the catfish diet, with the 25% substitution level yielding the best results. Wu Yanyan [31] studied the impact of Lactobacillus acidophilus-fermented cottonseed meal on the growth performance, blood biochemical parameters, and immune indicators of AA broiler chickens. The experiment concluded that adding 6% Lactobacillus acidophilus-fermented cottonseed meal to the diet significantly boosted chicken growth, improved blood biochemical markers, and enhanced immune function. Xu Xingjun [32] utilized potato-fermented feed to nourish meat rabbits, discovering that this feed promoted weight gain, reduced feed consumption, and improved both protein utilization efficiency and fat content in rabbit meat. Yang Baochun [33] observed that young rabbits fed fermented feed exhibited significantly higher daily weight gains than those in the control group (P < 0.05).

 

5. Existing Issues and Research Hotspots

 

　　Currently, the main challenges in producing fermented feed include: 1. Different microbial strains exhibit varying fermentation characteristics and processes, yet the nutritional properties of the resulting fermented feed remain insufficiently studied. 2. The mechanisms by which fermented feed derived from different strains affects the growth of various animal species are not clearly understood. 3. A comprehensive safety evaluation system for fermented feed has yet to be established. Therefore, to advance the production of fermented feed, it is essential to develop a robust, scientifically sound evaluation framework that assesses both nutritional quality and hygiene standards. Additionally, more in-depth research is needed to tailor fermented feed formulations—selecting specific microbial strains and optimizing fermentation processes—to meet the unique growth requirements of different animals. This approach will not only ensure safer, more reliable feed options but also enhance the efficient utilization of feed ingredients.

 

References

 

　　[1] Pan Li. Food Fermentation Engineering [M]. Beijing: Chemical Industry Press, 2006.

 

　　[2] Zhou Lihong, Xu Zirong. Application of Biotechnology in Animal Husbandry and the Feed Industry [J]. China Feed, 2004, (19): 7–9.

 

　　[3] Zhang Heng, Liu Lihé, He Guolong. Research and Application of Solid-State Fermentation Technology in Feed Resource Development [J]. Contemporary Aquaculture, 2011, (7): 66–69.

 

　　[4] Deng Lufang, Fan Xueshan, Wang Jiaqi. Research Advances in Microbial Fermentation of Protein Feed from Oilseed Meals [J]. Chinese Journal of Animal and Veterinary Sciences, 2011, (6): 25–30.

 

　　[5] Ma Wenqiang, Feng Jie, Liu Xin. Study on Nutritional Characteristics of Microbial-Fermented Soybean Meal [J]. Journal of Cereals and Oils, 2008, (1): 121–124.

 

　　[6] Mo Zhongwen, Huang Gang. Research on Producing Fermented Soybean Meal via Solid-State Fermentation [J]. China Oils & Fats, 2007, (7): 38–40.

 

　　[7] Yang Xu, Cai Guolin, Cao Yu, et al. Optimization of Conditions for Enhancing Soybean Meal Protein Content via Solid-State Fermentation [J]. China Brewing, 2008, (5): 17–20.

 

　　[8] Zhuge Bin, Liu Jun, Fang Huiying, et al. Study on the Process and Synergistic Effects of Mixed-Microbe Fermentation for Improving Cottonseed Meal Protein [J]. China Biotechnology Journal, 2011, (9): 62–68.

 

　　[9] Qiao Xiaoyan, Cai Guolin, Lu Jian. Study on Improving the Feed Quality of Cottonseed Meal through Microbial Fermentation [J]. China Oils & Fats, 2013, (5): 30–34.

 

　　[10] Xia Pengbo, Tang Jiangwu, Liang Yunxiang. Screening of Detoxifying Strains from Cottonseed Meal and Optimization of Fermentation Conditions [J]. Zhejiang Agricultural Sciences, 2009, (1): 120–122.

 

　　[11] Jin Hongchun, Lan Shile, Hu Yi, et al. Study on Nutritional Changes in Cottonseed Meal Before and After Fermentation [J]. Feed Industry, 2011, (13): 19–23.

 

　　[12] Wang Gang, Cai Guolin, Lu Jian. Research on Improving Rapeseed Meal Quality Through Microbial Fermentation [J]. China Oils & Fats, 2011, (7): 39–41.

 

　　[13] Lu Yu, Yu Bo, Cang Chao, et al. Optimization Study on the Detoxification Process of Fermented Rapeseed Meal [J]. Food Science, 2007, (10): 267–271.

 

　　[14] Sun Lin, Li Lvmu, Zhang Banghui, et al. Study on Multi-Strain Solid-State Fermentation of Rapeseed Meal [J]. Journal of Cereals and Oils, 2009, (1): 85–89.

 

　　[15] Rao Hui. Research and Application Progress of Microbial Fermented Feed from Straw Resources at Home and Abroad [J]. Anhui Agricultural Science, 2009, (37): 159–161.

 

　　[16] Huang Qian, Huang Fenghong, Jiang Mulan, et al. Screening of Lignin-Degrading Microorganisms and Study on Straw Degradation via Mixed-Microbial Fermentation [J]. China Biotechnology Journal, 2008, (2): 66–70.

 

　　[17] Li Riqiang, Wang Aiying, Ge Zhian. Study on Solid-State Fermentation of Corn Stalks for Producing Feed Protein Fermentation Medium [J]. Journal of Agricultural Environmental Science, 2008, (6): 10–12.

 

　　[18] Wang Yiming. Study on Producing Single-Cell Protein Feed from Wheat Straw via Mixed-Microbe Solid-State Fermentation [D]. Gansu Agricultural University, 2009.

 

　　[19] Dong Xiaoli, Zhang Naifeng, Mu Litian, et al. Advances in the Application of Modern Biotechnology in Feed Resource Development [J]. Pig Industry Science, 2011, (8): 28–30.

 

　　[20] Hu Yongmei, Ai Shen, Ding Yimin, et al. Study on the Raw Material Fermentation Process of Bagasse Feed [J]. Feed Industry, 2006, (17): 27–29.

 

　　[21] Xu Yafei. Study on Producing Fermented Feed Using Bagasse and Sugarcane Molasses [D]. Guangxi University, 2007.

 

　　[22] Zhang Changxia. Study on Producing Protein Feed from Apple Pomace via Mixed-Microbe Solid-State Fermentation [D]. Tianjin University of Science and Technology, 2004.

 

　　[23] Wang Xiaorong. Study on Producing Protein Feed through Fermentation of Wet Oil Tea Seed Residue [D]. Hunan Agricultural University, 2012.

 

　　[24] Peng Zhongli, Guo Chunhua, Bai Xue, et al. The Effect of Microbial Fermented Feed on Goat Production Performance [J]. Guizhou Agricultural Sciences, 2013, (6): 41–43.

 

　　[25] Lin Biaosheng, Luo Jian, Dai Ailing, et al. The Effect of Microbial Fermented Feed on Growth Performance of Weaned Piglets [J]. Anhui Agricultural Science, 2010, (5): 2378–2380.

 

　　[26] Jin Zhuang, Peng Jian, Hu Xinwen, et al. Effects of Lactic Acid Bacteria-Fermented Feed on the Performance of Growing Pigs [J]. Grain & Feed Industry, 2010, (3): 89–91.

 

　　[27] Zhai Hengxiao, Lü Songqiao, Guo Xiaohua, et al. Effects of Fermented Feed on the Production Performance of Growing-Finishing Pigs [J]. Feed & Animal Husbandry, 2008, (8): 31–32.

 

　　[28] Qiu Juan. The Effect of Bio-fermented Feed on Growth Performance of Piglets [J]. Fujian Agricultural Science and Technology, 2011, (2): 51–52.

 

　　[29] Huang Shijin, Feng Xiangren, Zhou Yong. Application Study of Compound Microbial Fermented Feed in Tilapia Aquaculture [J]. Southern Agriculture Journal, 2011, (8): 1003–1006.

 

　　[30] Li Hui, Huang Feng, Hu Bing. Effects of Fermented Soybean Meal Substituting Fish Meal on Growth and Apparent Feed Digestibility in Channel Catfish [J]. Freshwater Fisheries, 2007, (5): 41–44.

 

　　[31] Wu Yanyan, Zhang Wenju, Nie Cunxi, et al. Effects of Fermented Cottonseed Meal on Growth Performance, Blood Biochemical Parameters, and Immune Function in Broilers [J]. Feed Research, 2013, (8): 37–40.

 

　　[32] Xu Xingjun, Zhang Weiwei, Lü Jianwei, et al. Effects of Potato Residue Fermented Feed on the Production Performance and Meat Quality of Meat Rabbits [J]. Anhui Journal of Agricultural Science, 2009, (11): 5005–5006.

 

　　[33] Yang Baochun. The Effect of EM Fermented Feed on Weight Gain in Young Rabbits [J]. Heilongjiang Journal of Animal Science and Veterinary Medicine, 2002, (11): 51–53.

 

(Pictured are Kong Ling from the Biotechnology Department of Chengdu Dadi Hank Bio-Technology Co., Ltd., and DDC, the author of this article.) Deputy General Manager Bao Qingbin at DDC The biology lab is holding a discussion on experimental plans. Please credit the source when sharing or reprinting this article.