Probiotics are live microorganisms that provide health benefits to the host when consumed in adequate concentrations. The strains most frequently used as probiotics include Lactobacillus and Bifidobacteria. Probiotics have demonstrated significant potential as therapeutic options for various diseases. In addition to oligosaccharides, proteins, hydrolysates and peptides have also been shown function as prebiotics to promote the growth of probiotics. Therefore, this review provides a summary of the available information and current knowledge on the effects of various proteins on probiotics, focusing on how proteins influence probiotics, although uncertainties and disagreements about how the metabolism of proteins promotes probiotics still exist. Understanding the relationship between proteins and probiotics will allow appropriate prebiotic selection and the development of effective methods to promote the proliferation of probiotics.

Soybean dreg is a by-product of soybean products production, with a large consumption in China. Low utilization value leads to random discarding, which is one of the important sources of urban pollution. In this work, porous biochar was synthesized using a one-pot method and potassium bicarbonate (KHCO₃) with low-cost soybean dreg (SD) powder as the carbon precursor to investigating the adsorption of methylene blue (MB). The prepared samples were characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM), elemental analyzer (EA), Brunauer-Emmett-Teller (BET), X-ray diffractometer (XRD), Raman spectroscopy (Raman), Fourier transform infrared spectrometer (FTIR), and X-ray photoelectron spectroscopy (XPS). The obtained SDB-K-3 showed a high specific surface area of 1620 m² g⁻¹, a large pore volume of 0.7509 cm³ g⁻¹, and an average pore diameter of 1.859 nm. The results indicated that the maximum adsorption capacity of SDB-K-3 to MB could reach 1273.51 mg g⁻¹ at 318 K. The kinetic data were most consistent with the pseudo-second-order model and the adsorption behavior was more suitable for the Langmuir isotherm equation. This study demonstrated that the porous biochar adsorbent can be prepared from soybean dreg by high value utilization, and it could hold significant potential for dye wastewater treatment in the future.

Bifidobacterium is a common probiotic that plays a vital role in the intestinal tract. This study aimed to explore the different effects of soybean protein and soybean peptides on the growth and metabolism of Bifidobacterium animalis subsp. animalis JCM 1190. Soybean protein and soybean peptides were digested in vitro, after which different nitrogen source containing media were prepared and used for the monoculture of Bifidobacterium animalis subsp. animalis JCM 1190 and the co-culture of Bifidobacterium animalis subsp. animalis JCM 1190 and Escherichia coli JCM 1649. During the culture process, the viable cell number and lactic acid and acetic acid contents were measured, while non-targeted metabonomics was used to detect the differential metabolites and metabolic pathways. The results showed that soybean protein and soybean peptides promoted the growth and metabolism of Bifidobacterium animalis subsp. animalis JCM 1190, while digested soybean peptides had a better effect. Digested soybean peptides increased the viable cell number and lactic acid and acetic acid contents in the monoculture by regulating glycine, serine, and threonine metabolism, as well as pyruvate metabolism, the TCA cycle, glycolipid metabolism, and other metabolic pathways, balanced the ability of Bifidobacterium animalis subsp. animalis JCM 1190 and Escherichia coli JCM 1649 to utilize nitrogen sources during the early period and enhanced the competitiveness of Bifidobacterium animalis subsp. animalis JCM 1190 during the later period in co-culture.

Soybean protein (Pro) and soybean oligopeptide (Pep) were subjected to simulated digestion in vitro to study the effect of Pep on the growth and metabolism of Lactobacillus acidophilus JCM 1132. First, the molecular weight distribution differences of samples before and after digestion were compared, and the samples were used to replace the nitrogen source components in the culture media. Then, the viable cell numbers, lactic acid and acetic acid content, differential metabolites, and metabolic pathways during the culturing process were measured. Results showed that the digested soybean oligopeptide (dPep) was less efficient than MRS medium in promoting the growth, but by increasing the content of the intermediates during the tricarboxylic acid (TCA) cycle, its metabolic capacity was significantly improved. Besides, due to the low molecular weight of dPep, it can be better transported and utilized. And dPep significantly strengthened the amino acid metabolism and weakened the glycerol phospholipid metabolism, so the ability of dPep in promoting the growth and metabolism of Lactobacillus acidophilus JCM 1132 is higher than the digested soybean protein (dPro).