Maajid Hafidh Shofwan, Nurliyani Nurliyani, Widodo Widodo
Faculty of Animal Science, Universitas Gadjah Mada, Yogyakarta, Indonesia.
AIMS Microbiol. 2022 Apr 25;8(2):138-152. doi: 10.3934/microbiol.2022012. eCollection 2022.
This study evaluated the ability of two strains of bacterial starter cultures, AP (AP) and AG (AG), to produce exopolysaccharides (EPSs). First, the physicochemical properties of the fermented milk produced by AP and AG were assessed, including physical qualities like viscosity and syneresis and chemical qualities, such as pH, acidity, protein, lactose, fat content, and total solid. Then, AP and AG's ability to produce EPS was measured. Additionally, the EPS' microstructure was observed using a scanning electron microscope, and its chemical structure was assessed using Fourier transform-infrared (FT-IR) spectroscopy. Also, AP and AG's ability to produce EPS was tracked at the molecular level by studying the glycosyltransferase () gene. Statistical analysis showed that the milk fermented using AP and AG had similar physicochemical qualities (P > 0.05) but significantly different physical qualities (P < 0.05). Additionally, the milk fermented with AP had lower viscosity (1137.33 ± 34.31 centiPoise) than AG (1221.50 ± 20.66 centiPoise). In addition, the milk fermented using AP had higher syneresis (19.42%) than AG (17.83%). The higher viscosity and lower syneresis in the milk fermented using AG were associated with AG's ability to produce more EPS (1409 mg/L) than AP (1204 mg/L). In addition, according to the FT-IR analysis, the AP- and AG-synthesized EPS contained absorption bands at 3323, 2980, 2901, 1642, 1084, 1043, and 873 cm. The absorption band at 1642 and 2980 cm corresponds to carbonyl and methylene groups, respectively. Absorption band 873 cm is characteristic of the α-glycosidic bond of α-glucan in EPS. Moreover, the absorption bands on the wavelength region corresponding to the functional groups in the AP- and AG-produced EPS were similar to those in commercially available EPS. Lastly, , contributing to EPS synthesis, was found in the genomes of AP and AG, suggesting the role of glycosyltransferase in the EPS synthesis by both strains.
本研究评估了两种细菌发酵剂菌株AP和AG产生胞外多糖（EPS）的能力。首先，评估了由AP和AG生产的发酵乳的物理化学性质，包括诸如粘度和脱水收缩等物理性质以及诸如pH值、酸度、蛋白质、乳糖、脂肪含量和总固体等化学性质。然后，测定了AP和AG产生EPS的能力。此外，使用扫描电子显微镜观察了EPS的微观结构，并使用傅里叶变换红外（FT-IR）光谱评估了其化学结构。另外，通过研究糖基转移酶（）基因在分子水平上追踪了AP和AG产生EPS的能力。统计分析表明，使用AP和AG发酵的牛奶具有相似的物理化学性质（P>0.05），但物理性质有显著差异（P<0.05）。此外，用AP发酵的牛奶粘度（1137.33±34.31厘泊）低于AG（1221.50±20.66厘泊）。另外，用AP发酵 的牛奶脱水收缩率（19.42%）高于AG（17.83%）。使用AG发酵的牛奶中较高的粘度和较低的脱水收缩率与AG产生比AP更多EPS（1409毫克/升）的能力有关。此外，根据FT-IR分析，AP和AG合成的EPS在3323、2980、2901、1642、1084、1043和873厘米处有吸收带。1642和2980厘米处的吸收带分别对应于羰基和亚甲基。873厘米处的吸收带是EPS中α-葡聚糖的α-糖苷键的特征。此外，AP和AG产生的EPS中与官能团对应的波长区域上的吸收带与市售EPS中的吸收带相似。最后，在AP和AG的基因组中发现了有助于EPS合成的，这表明糖基转移酶在两种菌株的EPS合成中发挥作用。
