An alternative method for the decoloration of ɛ-poly-l-lysine eluate by macroporous resin in the separation and purification of ɛ-poly-l-lysine from fermentation broth

Decoloration and alkaloid enrichment of Dactylicapnos scandens extracts based on the use of strong anion-exchange resins in tandem with strong cation-exchange silica-based materials

Alkaloids are natural bioactive ingredients but are usually present in low amounts in plant extracts. In addition, the dark color of plant extracts increases the difficulty in separation and identification of alkaloids. Therefore, effective decoloration and alkaloid enrichment methods are necessary for purification and further pharmacological studies of alkaloids. In this study, a simple and efficient strategy is developed for the decoloration and alkaloid enrichment of Dactylicapnos scandens (D. scandens) extracts. In feasibility experiments, we evaluated two anion-exchange resins and two cation-exchange silica-based materials with different functional groups using a standard mixture composed of alkaloids and nonalkaloids. By virtue of its high adsorbability of nonalkaloids, the strong anion-exchange resin PA408 is considered a better choice for the removal of nonalkaloids, and the strong cation-exchange silica-based material HSCX was selected for its great adsorption capacity for alkaloids. Furthermore, the optimized elution system was applied for the decoloration and alkaloid enrichment of D. scandens extracts. Nonalkaloid impurities in the extracts were removed by the use of PA408 in tandem with HSCX treatment, and the total alkaloid recovery, decoloration and impurity removal ratios are determined to be 98.74%, 81.45% and 87.33%, respectively. This strategy can contribute to further alkaloid purification and pharmacological profiling of D. scandens extracts, as well as other plants with medicinal value.

Biotechnological production and application of epsilon-poly-L-lysine (ε-PL): biosynthesis and its metabolic regulation

Epsilon-poly-L-lysine (ε-PL) is an unusual biopolymer composed of L-lysine produced by several microorganisms, especially by the genus Streptomyces. Due to its excellent antimicrobial activity, good water solubility, high safety, and biodegradable nature, ε-PL with a GRAS status has been widely used in food and pharmaceutical industries. In the past years, studies have focused on the biotechnological production of ɛ-PL, the biosynthetic mechanism of microbial ɛ-PL, and its application. To provide new perspectives from recent advances, the review introduced the methods for the isolation of ɛ-PL producing strains and the biosynthetic mechanism of microbial ɛ-PL. We summarized the strategies for the improvement of ɛ-PL producing strains, including physical and chemical mutagenesis, ribosome engineering and gene engineering, and compared the different metabolic regulation strategies for improving ɛ-PL production, including medium optimization, nutrient supply, pH control, and dissolved oxygen control. Then, the downstream purification methods of ɛ-PL and its recent applications in food and medicine industries were introduced. Finally, we also proposed the potential challenges and the perspectives for the production of ε-PL.

Extraction and purification of ε-poly-l-lysine from fermentation broth using an ethanol/ammonium sulfate aqueous two-phase system combined with ultrafiltration

ε-Poly-l-lysine (ε-PL) serves as a natural food preservative and is manufactured mainly by extraction from microbial fermentation broth using ion-exchange chromatography. In order to develop an alternative purification strategy, an environmentally friendly alcohol/salt aqueous two-phase system (ATPS) was explored in this study for ε-PL extraction. A study of the separation of ε-PL in different alcohol/salt systems showed that ethanol/ammonium sulfate ATPS exhibited the highest ε-PL partition coefficient and recovery ratio. Based on the phase diagram, the effect of phase composition on partition, and the removal of pigment and protein, an ATPS that was composed of 20% (w/w) ethanol and 20% (w/w) ammonium sulfate, with a feedstock at pH 9.5, was developed to extract ε-PL from the fermentation broth. This achieved an ε-PL recovery ratio of 96.15% with an ε-PL purity of 40.23% after triplicate extractions. Subsequently, desalting by ultrafiltration led to a final ε-PL product of 92.39% purity and 87.72% recovery. The ethanol/ammonium sulfate ATPS provides a new possibility for ε-PL purification.

Simultaneous decolorization and deproteinization of α,ω-dodecanedioic acid fermentation broth by integrated ultrafiltration and adsorption treatments

α,ω-Dicarboxylic acids (DC) are versatile chemical intermediates with different chain length. For biosynthesis of DC, to obtain the highly pure product via crystallization, it is required to remove pigments and proteins in fermentation broth. However, a trade-off between decolorization/deproteinization ratio and DC recovery during the purification process was found, which impeded DC production by fermentation. When ultrafiltration (UF) was applied to treat α,ω-dodecanedioic acid (DC₁₂) broth, 93.4% of DC₁₂ recovery, 80.5% of decolorization ratio and 61.7% of deproteinization ratio were achieved by a PES 3 membrane. However, the membrane technology could not effectively retain the pigments or proteins with low molecular weight when a high DC₁₂ permeation was required. Meanwhile, the selected activated charcoal or macroporous resins were not good adsorbents for the present system. Furthermore, an integrated process for decolorization and deproteinization was developed. After filtration with PES3 membrane, an activated charcoal was used to remove the small proteins and pigments in the UF permeate. As a result, 91.4% of DC₁₂ recovery, 94.7% of decolorization ratio and 84.8% of deproteinization ratio were obtained by such two-stage strategy. These results would serve as a valuable guide for process design and practical operation in subsequent industrial application.