Bacillus licheniformis strain ZF-02 and application thereof in leaching iron from iron-rich kaolin

Abstract

The present application relates to a bacillus lactis ZF-02 and its application. The strain is preserved in Guangdong Microbial Culture Collection Center, the address of the preservation unit is No. 59 Building, 5th Floor, Guangzhou Xianlie Middle Road 100, the preservation time is October 27, 2025, and the preservation number is GDMCC No. 66772. The present application uses the deep interaction between bacillus lactis (Bacillus lactis) Sporolactobacillus putidus ) and minerals, uses iron-reducing bacteria metabolic products to dissolve iron minerals, destroys the mineral lattice, and thus dissolves impurity components, so as to provide a new idea for promoting the development of kaolin iron removal and whitening towards the direction of green, high efficiency and low carbon.

Description

Technical Field

[0001] This invention relates to the field of deep processing of non-metallic minerals, specifically to a strain of Lactobacillus spores ZF-02 and its application in leaching iron from iron-rich kaolin. Background Technology

[0002] The application value of kaolin largely depends on its whiteness, and iron impurities are the most significant factor affecting whiteness. Iron oxides, hydroxides, or hydrated oxides can give kaolin a yellow to reddish hue, while also reducing its natural and calcined whiteness. Therefore, iron removal and whitening are crucial steps in achieving high-value utilization of kaolin.

[0003] From a mineral composition perspective, kaolinite is mainly composed of kaolinite group minerals, often accompanied by quartz, feldspar, iron minerals, titanium minerals, and organic matter. The state of iron occurrence directly determines the direction of iron removal processes. Existing research classifies iron into two categories: one is "structural iron" embedded in the kaolinite crystal lattice, which is difficult to remove using conventional methods; the other is "free iron" in independent mineral forms, such as magnetite, hematite, limonite, siderite, pyrite, ilmenite, and jaundice, which are the main targets of current iron removal and whitening processes.

[0004] Each of the commonly used iron removal and whitening methods in industry has its own applicable limitations and shortcomings: Magnetic separation relies on differences in magnetic properties to separate iron minerals. It is effective for strongly magnetic minerals (such as magnetite) and is environmentally friendly, low-cost, and suitable for large-scale production. However, its separation ability is significantly insufficient for weakly magnetic or non-magnetic iron minerals (such as some forms of hematite and limonite).

[0005] Reduction bleaching utilizes sodium dithionite to reduce ferric iron to soluble ferrous iron under acidic conditions (pH 2–3), which is then removed by washing. This method can achieve deep whitening, but when the Fe2O3 content in the raw ore is high, the iron removal efficiency becomes a bottleneck, and the reagent cost is high. Furthermore, it generates acidic waste gas and wastewater, resulting in a heavy environmental burden.

[0006] Although the magnetic separation-reduction bleaching combined method reduces acid consumption and improves overall efficiency to some extent, it does not fundamentally solve the environmental pollution problem caused by acid bleaching.

[0007] For iron-rich kaolin (i.e., low-grade resources) with high iron content, the above methods are often not very effective in removing iron and whitening, or require a significant increase in the amount of reagents used, which leads to a decline in both economic efficiency and environmental friendliness, thus restricting the high-value utilization of such resources.

[0008] Against this backdrop, bio-beneficiation technology has attracted some attention. This technology utilizes microorganisms such as bacteria to enrich, separate, and extract useful components from minerals, offering significant advantages such as low cost, low energy consumption, and environmental friendliness. However, current research on the application of microbial methods in the iron removal and purification of kaolin remains very limited, and related reports are scarce. Summary of the Invention

[0009] The purpose of this invention is to provide a strain of Lactobacillus spores ZF-02 and its application in leaching iron from iron-rich kaolin.

[0010] A strain of Lactobacillus spores ( Sporolactobacillus putidus ZF-02, this strain is deposited at the Guangdong Provincial Center for Microbial Culture Collection, located at 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou, on October 27, 2025, with accession number GDMCC No. 66772.

[0011] Application of the above-mentioned strains in removing iron from iron-rich kaolin.

[0012] Furthermore, it includes the following steps: S1. Prepare a bacterial suspension of Bacillus sporulation Lactobacillus ZF-02; S2. After mixing iron-rich kaolin, bacterial suspension, water, carbon source, and nitrogen source, leach and culture the mixture to remove iron from the iron-rich kaolin.

[0013] Furthermore, based on the mass ratio, the ratio of iron-rich kaolin: bacterial suspension: water: carbon source: nitrogen source = 1:0.001-0.003:0.3-0.4:0.003-0.005:0.001-0.003; The carbon source is one of starch, cellulose, molasses, sodium acetate, mannitol, sucrose, maltose, xylose, and lactose. The nitrogen source is one of the following: peptone, beef extract, yeast powder, soybean meal, NH4Cl4, potassium nitrate, ammonium nitrate, or glutamic acid.

[0014] Furthermore, the leaching culture was carried out at a temperature of 20℃-25℃ for 3-12 days.

[0015] A method for removing iron from iron-rich kaolin through bioleaching includes the following steps: S1. Prepare a bacterial suspension of Lactobacillus ZF-02 as described in claim 1; S2. After mixing iron-rich kaolin, bacterial suspension, water, carbon source, and nitrogen source, the mixture is cultured for a period of time to complete the leaching reaction. S3. After the leaching reaction is complete, the raw kaolin ore slurry is taken out, screened, and then the kaolin coarse concentrate slurry is obtained. The kaolin coarse concentrate slurry is then classified and dewatered in sequence to obtain iron-removed kaolin.

[0016] Furthermore, in S2, the mass ratio of iron-rich kaolin: bacterial suspension: water: carbon source: nitrogen source is 1:0.001-0.003:0.3-0.4:0.003-0.005:0.001-0.003; The carbon source is one of starch, cellulose, molasses, sodium acetate, mannitol, sucrose, maltose, xylose, and lactose. The nitrogen source is one of the following: peptone, beef extract, yeast powder, soybean meal, NH4Cl4, potassium nitrate, ammonium nitrate, or glutamic acid.

[0017] Furthermore, in S2, the leaching culture temperature conditions were 20℃-25℃, and the time conditions were 3-12 days.

[0018] The beneficial effects achieved by this invention are: (1) The Lactobacillus ZF-02 of the present invention is a highly efficient iron-reducing bacterium that can utilize its metabolites to remove Fe from iron-rich kaolin through deep interaction with it. 3+ Reduced to soluble Fe 2+ After forming a soluble complex, it is removed, thereby achieving lattice destruction and impurity dissolution; this method provides a green, low-carbon, and efficient new path for iron removal and whitening of kaolin.

[0019] (2) The Bacillus spores ZF-02 of the present invention has a strong iron removal ability on iron-rich kaolin, with an iron removal rate of over 90%. Along with the removal of iron impurities, the whiteness of the kaolin is greatly improved, indicating that Bacillus spores ZF-02 can efficiently treat low-grade iron-rich kaolin with high iron content, greatly improving its resource utilization value. It overcomes the bottleneck problems of unsatisfactory effect, large amount of reagents, and serious environmental pollution of traditional magnetic separation, reduction bleaching and other methods when treating iron-rich ore, and has good prospects for industrial application. Attached Figure Description

[0020] Figure 1 The present invention is based on the spore-forming Lactobacillus ( Sporolactobacillus putidus Phylogenetic tree of ZF-02; Figure 2 The present invention is based on the spore-forming Lactobacillus ( Sporolactobacillus putidus Colony morphology diagram of ZF-02; Figure 3 This is a process flow diagram of a bioleaching method for removing iron from iron-rich kaolin. Detailed Implementation

[0021] The present invention will be further illustrated by the following examples. The preferred examples described herein are for illustrative and explanatory purposes only. The technical means used in the examples are known to those skilled in the art, and the instruments and reagents used are commercially available.

[0022] The first thing this invention aims to protect is a strain of *Lactobacillus spores* (…). Sporolactobacillus putidus Lactobacillus ZF-02 is deposited at the Guangdong Provincial Center for Microbial Culture Collection, located at 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou, on October 27, 2025, with accession number GDMCC No. 66772.

[0023] The *Lactobacillus spores* ZF-02 strain of this invention was initially isolated from raw ore samples collected from the Shange mining area in Shange Town, Maoming City, Guangdong Province. The colony morphology of the *Lactobacillus spores* ZF-02 is as follows: Figure 1 As shown. By Figure 1 It is known that the colonies of the Bacillus spores ZF-02 are generally white to light gray, with a fluffy or cottony texture, and spread evenly radially from the center to the periphery, with fine whiskers or tree-like edges; the culture dish has no obvious odor.

[0024] The 16S rDNA sequence of *Lactobacillus sporogenes* ZF-02 was compared with sequences in the GenBank database using BLAST analysis, and a phylogenetic tree of *Lactobacillus sporogenes* ZF-02 was constructed, as follows: Figure 2 As shown. Based on phylogenetic tree analysis, morphological analysis, and the physiological and biochemical characteristics of this strain, strain ZF-02 was identified as *Lactobacillus sporogenes*. Sporolactobacillus putidus ).

[0025] It should be noted that the screening, isolation, culture and identification of Bacillus spores ZF-02 in this invention are all existing technologies, and will not be described in detail in this invention.

[0026] The second aspect of this invention is the application of Bacillus spores ZF-02, specifically its application in removing iron from iron-rich kaolin. The iron-rich kaolin described in this invention refers to kaolin deposits formed from aluminosilicate parent rocks through in-situ deep chemical weathering, without transportation, or deposits that are first deposited and then weathered. Its main mineral component is kaolinite, accompanied by a large amount of primary mineral residues such as quartz and incompletely weathered feldspar. Iron impurities mainly exist in the form of free oxides or hydroxides (Fe2O3 content is usually 1%-12%). The ore generally has the characteristics of being mixed with mud and sand and having a loose structure.

[0027] The above application specifically includes the following steps: S1. Preparation of Lactobacillus spores ZF-02 bacterial suspension: The Lactobacillus spores ZF-02 is cultured in a culture medium to obtain a fermentation broth; This invention does not have any special limitations on the type of culture medium, as long as it can enable Lactobacillus spores ZF-02 to grow normally.

[0028] In this invention, the culture medium is preferably TSB medium, LB medium, liquid fermentation medium, aniline blue medium, phosphorus-solubilizing fermentation medium, or lignin enrichment medium, more preferably LB medium. In this invention, the pH value of the culture medium is preferably 4–10, more preferably 5–9, and even more preferably 5.

[0029] In this invention, if the culture medium is LB medium, the culture medium preferably also includes a carbon source with a mass percentage of 0.1% and a nitrogen source with a mass percentage of 0.01%.

[0030] In this invention, the carbon source preferably includes one or more of starch, cellulose, molasses, grape pomace, sodium acetate, mannitol, sucrose, maltose, xylose, and lactose, more preferably starch; the nitrogen source preferably includes one or more of peptone, beef extract, yeast powder, soybean meal, NH4Cl4, potassium nitrate, ammonium nitrate, and glutamic acid, more preferably peptone. The culture temperature is preferably 15℃~45℃, more preferably 20℃~25℃, and even more preferably 22℃; the culture time is preferably 2-7 days, and even more preferably 3 days; the liquid volume during the culture is preferably 50-150mL, more preferably 50-100mL, and even more preferably 50mL. In this invention, the culture is preferably carried out in a shaker, and the rotation speed of the shaker is preferably 150-200rpm, and even more preferably 180rpm.

[0031] S2. After mixing iron-rich kaolin, bacterial suspension, water, carbon source, and nitrogen source, the mixture is cultured to remove iron from the iron-rich kaolin.

[0032] Specifically, by mass ratio, the ratio of iron-rich kaolin: bacterial suspension: water: carbon source: nitrogen source is 1:0.001-0.003:0.3-0.4:0.003-0.005:0.001-0.003.

[0033] The carbon source is one of starch, cellulose, molasses, sodium acetate, mannitol, sucrose, maltose, xylose, and lactose. The nitrogen source is one of the following: peptone, beef extract, yeast powder, soybean meal, NH4Cl4, potassium nitrate, ammonium nitrate, or glutamic acid.

[0034] The incubation temperature is 15-45℃, and the incubation time is 3-12 days.

[0035] During iron reduction, the organic acids, reducing sugars, and amino acids produced by fermentation with Bacillus spores ZF-02 work together to reduce Fe³⁺. + The strain utilizes reduction and complexation to achieve efficient iron removal. Test results show that this strain can remove up to 94.78% of iron from iron-rich kaolin.

[0036] <Example 1> The application of Bacillus spores ZF-02 in removing iron from iron-rich kaolin clay includes the following methods: S1. Prepare a bacterial suspension of Bacillus sporulation Lactobacillus ZF-02; S2. Weigh 1 kg of iron-rich kaolin, 300 g of water, 2 g of bacterial suspension, 5 g of starch, and 3 g of peptone. Mix and culture the microbial slurry at 22°C for 9 days.

[0037] The whiteness and Fe2O3 content of the microbial slurry were tested on days 0, 3, 6 and 9, and the results are shown in Table 1.

[0038] Table 1

[0039] As shown in Table 1, on the 9th day, the iron removal rate in the microbial slurry reached 94.73%, the Fe2O3 content decreased from 9.87% to 0.52%, and the burnt white content increased from 22.6% to 90.2%.

[0040] <Example 2> The application of Bacillus spores ZF-02 in removing iron from iron-rich kaolin clay includes the following methods: S1. Prepare a bacterial suspension of Bacillus sporulation Lactobacillus ZF-02; S2. Weigh 1 kg of iron-rich kaolin, 300 g of water, 2 g of bacterial suspension, 4 g of starch, and 2 g of peptone. Mix and culture the microbial slurry at 21°C for 12 days.

[0041] The microbial slurry was cultured at 20°C for 12 days.

[0042] The whiteness and Fe2O3 content of the microbial slurry were tested on days 0, 3, 6, 9 and 12, and the results are shown in Table 2.

[0043] Table 2

[0044] Table 2 shows that on day 9, the iron removal rate in the microbial slurry reached 92.65%, the Fe2O3 content decreased from 8.43% to 0.62%, and the whiteness increased from 26.4% to 90.1%. On day 12, the iron removal rate in the microbial slurry reached 94.78%, the Fe2O3 content decreased from 8.43% to 0.44%, and the whiteness increased from 20.7% to 91.8%. This indicates that leaching iron removal treatment of iron-rich kaolin using Bacillus spores ZF-02 can significantly improve the utilization value of this low-grade kaolin resource.

[0045] <Example 3> The application of Bacillus spores ZF-02 in removing iron from iron-rich kaolin clay includes the following methods: S1. Prepare a bacterial suspension of Bacillus sporulation Lactobacillus ZF-02; S2. Weigh 10kg of iron-rich kaolin, 3500g of water, 22g of bacterial suspension, 50g of starch, and 25g of peptone. Mix and culture the microbial slurry at 22℃ for 12 days.

[0046] The whiteness and Fe2O3 content of the microbial slurry were tested on days 0, 3, 6, 9 and 12, and the results are shown in Table 3.

[0047] Table 3

[0048] As shown in Table 3, with the increase of leaching time, on the 12th day, the iron removal rate in the microbial slurry reached 94.67%, the Fe2O3 content decreased from 8.07% to 0.43%, and the burnt white content increased from 30.4% to 92.4%.

[0049] like Figure 3 As shown, the third aspect to be protected by this invention is a method for removing iron from iron-rich kaolin through bioleaching, specifically including the following steps: S1. Prepare a bacterial suspension of Bacillus sporulation Lactobacillus ZF-02; S2. Mix iron-rich kaolin, bacterial suspension, water, carbon source, and nitrogen source, and incubate for a period of time to complete the leaching reaction.

[0050] Specifically, by mass ratio, the ratio of iron-rich kaolin: bacterial suspension: water: carbon source: nitrogen source is 1:0.001-0.003:0.3-0.4:0.003-0.005:0.001-0.003.

[0051] The carbon source is one of starch, cellulose, molasses, sodium acetate, mannitol, sucrose, maltose, xylose, and lactose. The nitrogen source is one of the following: peptone, beef extract, yeast powder, soybean meal, NH4Cl4, potassium nitrate, ammonium nitrate, or glutamic acid.

[0052] The leaching culture temperature is 15-45℃, and the culture time is 3-12 days.

[0053] S3. After the leaching reaction is complete, the raw kaolin ore slurry is taken out and screened to remove coarse sand, thus obtaining kaolin coarse concentrate slurry. S4. After classifying and dewatering the kaolin coarse concentrate slurry, iron-removed kaolin is obtained. Specifically, during the classification process, the concentration of the kaolin coarse concentrate slurry is 63-78%.

[0054] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A strain of spore-forming Lactobacillus ( Sporolactobacillus putidus ZF-02, characterized in that, The Lactobacillus sporeans ZF-02 is deposited at the Guangdong Provincial Center for Microbial Culture Collection, located at 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou, on October 27, 2025, with accession number GDMCC No. 66772.

2. The application of the strain described in claim 1 in removing iron from iron-rich kaolin.

3. The application according to claim 2, characterized in that, Specifically, the following steps are included: S1. Prepare a bacterial suspension of Bacillus sporulation Lactobacillus ZF-02; S2. After mixing iron-rich kaolin, bacterial suspension, water, carbon source, and nitrogen source, leach and culture the mixture to remove iron from the iron-rich kaolin.

4. The application according to claim 3, characterized in that, Based on the mass ratio, the ratio of iron-rich kaolin: bacterial suspension: water: carbon source: nitrogen source = 1:0.001-0.003:0.3-0.4:0.003-0.005:0.001-0.003; The carbon source is one of starch, cellulose, molasses, sodium acetate, mannitol, sucrose, maltose, xylose, and lactose. The nitrogen source is one of the following: peptone, beef extract, yeast powder, soybean meal, NH4Cl4, potassium nitrate, ammonium nitrate, or glutamic acid.

5. The application according to claim 3, characterized in that, The leaching culture was carried out at a temperature of 20℃-25℃ for 3-12 days.

6. A method for removing iron from iron-rich kaolin through biological leaching, characterized in that, Specifically, the following steps are included: S1. Prepare a bacterial suspension of Lactobacillus ZF-02 as described in claim 1; S2. After mixing iron-rich kaolin, bacterial suspension, water, carbon source, and nitrogen source, the mixture is cultured for a period of time to complete the leaching reaction. S3. After the leaching reaction is complete, the raw kaolin ore slurry is taken out, screened, and then the kaolin coarse concentrate slurry is obtained. The kaolin coarse concentrate slurry is then classified and dewatered in sequence to obtain iron-removed kaolin.

7. The method for removing iron from iron-rich kaolin through bioleaching according to claim 6, characterized in that, In S2, the mass ratio of iron-rich kaolin: bacterial suspension: water: carbon source: nitrogen source is 1:0.001-0.003:0.3-0.4:0.003-0.005:0.001-0.

003.

8. The method for removing iron from iron-rich kaolin through bioleaching according to claim 7, characterized in that, The carbon source is one of starch, cellulose, molasses, sodium acetate, mannitol, sucrose, maltose, xylose, and lactose. The nitrogen source is one of the following: peptone, beef extract, yeast powder, soybean meal, NH4Cl4, potassium nitrate, ammonium nitrate, and glutamic acid.

9. The method for removing iron from iron-rich kaolin through bioleaching according to claim 6, characterized in that, In S2, the leaching culture temperature conditions were 20℃-25℃, and the time conditions were 3-12 days.

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