Insights into the simultaneous utilization of glucose and glycerol by Streptomyces albulus M-Z18 for high ε-poly-l-lysine productivity

Bioprocess and Biosystems Engineering - The simultaneous consumption of glucose and glycerol led to remarkably higher productivity of both biomass and ε-poly-l-lysine (ε-PL), which was of...     

Enhancement of ε-poly-l-lysine synthesis in Streptomyces by exogenous glutathione

Bioprocess and Biosystems Engineering - Our previous work indicated that the vigor of Streptomyces decreased at the later stage of ε-poly-l-lysine (ε-PL) fermentation. In this study, we...     

Production of ��-poly-l-lysine using a novel two-stage pH control strategy by Streptomyces sp. M-Z18 from glycerol

The production of ε-poly-l-lysine (ε-PL) by Streptomyces sp. M-Z18 from glycerol was investigated in a 5-L jar-fermenter. Batch fermentations by Streptomyces sp. M-Z18 at various pH values ranging from 3.5 to 4.5 were studied. Based on the analysis of the time course of specific cell growth rate and specific ε-PL formation rate, a novel two-stage pH control strategy was developed to improve ε-PL production by shifting the culture pH from 3.5 to 3.8 after 36 h of cultivation. By applying the strategy, the maximal ε-PL concentration and productivity had a significant improvement and reached 9.13 g L⁻¹ and 4.76 g L⁻¹ day⁻¹, respectively, compared with those in one-stage pH control process where the pH value is controlled at 3.5 (7.83 g L⁻¹ and 3.13 g L⁻¹ day⁻¹). Fed-batch fermentation with two-stage pH control strategy was also applied to produce ε-PL; final ε-PL concentration of 30.11 g L⁻¹ was obtained, being 3.3-fold greater than that of batch fermentation. To our knowledge, it is the first report on production of ε-PL from glycerol in fermenter scale and achievement of high ε-PL production with two-stage pH control strategy.     

Enhancement of ε-poly-l-lysine production by overexpressing the ammonium transporter gene in Streptomyces albulus PD-1

Bioprocess and Biosystems Engineering - The antibacterial polymer ɛ-poly-l-lysine (ε-PL) has been widely used as a safe food preservative. As the synthesis of ε-PL requires a rich...     

Enhanced ε-poly-l-lysine production by inducing double antibiotic-resistant mutations in Streptomyces albulus

Bioprocess and Biosystems Engineering - ε-Poly-l-lysine (ε-PL), as a food additive, has been widely used in many countries. However, its production still needs to be improved. We...     

Promotion of ε-poly-l-lysine production by iron in Kitasatospora kifunense

Kitasatospora kifunense, belonging to the Streptomycetaceae family, produces a basic homopolymer, ε-poly-l-lysine, which is used as a food preservative. We showed that ε-poly-l-lysine production in this bacterium on agar plates with iron started two or three days earlier than that on plates without iron. We also showed that iron added to a liquid culture medium increased ε-poly-l-lysine production by K. kifunense. Similarly, manganese and cobalt also promoted ε-poly-l-lysine production on agar plates. Moreover, cobalt promoted ε-poly-l-lysine production in liquid culture media. These results indicate that iron, manganese and cobalt are involved in regulating the ε-poly-l-lysine biosynthesis system in K. kifunense.     

Efficient production of ε-poly-l-lysine from glucose by two-stage fermentation using pH shock strategy

In this study, a pH shock strategy was employed to enhance ε-poly-l-lysine (ε-PL) production from glucose. In the conventional fermentation, in the early stage, only 13% of total ε-PL production is achieved in 25% of the entire fermentation period, which severely affected ε-PL productivity. To improve the efficiency of ε-PL production during fermentation, a novel two-stage fermentation, namely culture and fermentation stages, was proposed on the basis of the analysis of conventional pH shock fermentation. After optimization of parameters such as inoculum growth conditions, initial fermentation pH, and inoculum volume, the ε-PL production and productivity achieved using the novel fermentation process in a 5-L fermenter reached 32.22 g/L and 5.86 g/L/day, which were 32.3% and 36.6% higher, respectively, when compared with those obtained in conventional fermentation. Furthermore, evaluation of acid tolerance of mycelia collected from the pH shock fermentation showed that pH shock enhanced ε-PL production, which might be related to the acid tolerance of Streptomyces albulus and pH stress (pH 3.0). The results obtained could be useful for large-scale ε-PL production and to provide new information on ε-PL biosynthesis mechanism.     

Understanding high ε-poly-l-lysine production by Streptomyces albulus using pH shock strategy in the level of transcriptomics

Journal of Industrial Microbiology & Biotechnology - ε-Poly-l-lysine (ε-PL) is a natural food preservative, which exhibits antimicrobial activity against a wide spectra of...     

Metabolic analyses of the improved ε-poly-l-lysine productivity using a glucose–glycerol mixed carbon source in chemostat cultures

Bioprocess and Biosystems Engineering - The glucose–glycerol mixed carbon source remarkably reduced the batch fermentation time of ε-poly-l-lysine (ε-PL) production, leading to...     

Stoichiometric analysis and experimental investigation of glycerol–glucose co-fermentation in Klebsiella pneumoniae under microaerobic conditions

The ratio between two substrates is an important parameter in microbial co-fermentation, such as 1,3-propanediol production from glycerol by Klebsiella pneumoniae using glucose as the cosubstrate. In this study, the glycerol–glucose cometabolism by K. pneumoniae is stoichiometrically analyzed according to energy (ATP), reducing equivalent (NADH₂) and product balances. The theoretical analysis reveals that the yield of 1,3-propanediol to glycerol under microaerobic conditions depends not only on the ratio of glucose to glycerol initially added, but also on the molar fraction of reducing equivalent oxidized completely by molecular oxygen in tricarboxylic acid (TCA) cycle (δ) and the molar fraction of TCA cycle in acetyl-CoA metabolism (γ). The maximum ratio of 0.32 mol glucose per mol glycerol is needed to convert glycerol completely to 1,3-propanediol under anaerobic conditions if glycerol neither enters oxidation pathways nor forms biomass. The ratio can be reduced under microaerobic conditions. The experimental results of batch cultures demonstrate that the biomass concentration and yield of 1,3-propanediol on glycerol could be enhanced by using glucose as a co-substrate. The theoretical analysis reveals the relationship between yield of 1,3-propanediol to glycerol, ratio of glucose to glycerol and respiratory quotient (RQ). These results are helpful for the experimental design and control.     

Biosynthesis of poly(ɛ- l-lysine)s in two newly isolated strains of Streptomyces sp.

The biosynthesis of poly(ɛ-l-lysine) (ɛ-PL) in the two newly isolated strains of Streptomyces lydicus USE-11 (USE-11) and Streptomyces sp. USE-51 (USE-51) was studied by a newly developed two-stage culture method of cell growth at pH 6.8 and ɛ-PL production at pH 4.5. USE-11 synthesized ɛ-PL consisting of about 28 residues at a high production level, whereas USE-51 did the polymer with 15 ones at a low level. The secreted ɛ-PLs in culture media were digested in a neutral pH range with a peptide hydrolase(s) produced by the ɛ-PL producers. The optimum production levels were presumed to be dependent upon the inherent ɛ-PL synthesis machinery of each producer. The production in USE-51 was sharply dependent upon cell density as was often observed in the production of antibiotics, whereas that in USE-11 was scarcely affected by the density. The was found to be essential for the ɛ-PL production in both strains. This might suggest the involvement of a thiol group in the polymerization reactions including the activation of l-lysine. This study indicates that USE-11 is a most suitable strain for the exploration of the ɛ-PL biosynthesis at the molecular level as well as for the technical applications.Electronic supplementary material Electronic supplementary material is available if you access this article at and is accesible for authorized users.An erratum to this article can be found at     

Effect of growth rate on α-amylase production by Streptomyces sp. IMD 2679

The α-amylase of Streptomyces sp. IMD 2679 was subject to catabolite repression. Four different growth rates were achieved when the organism was grown at 40 °C and 55 °C in the presence and absence of cobalt, with an inverse relationship between α-amylase production and growth rate. Highest α-amylase yields (520 units/ml) were obtained at the lowest growth rate (0.062 h⁻¹), at 40 °C in the absence of cobalt, while at the highest growth rate (0.35 h⁻¹), at 55 °C in the presence of cobalt, α-amylase production was decreased to 150 units/ml. As growth rate increased, the rate of specific utilisation of the carbon source maltose also increased, from 46 to 123 μg maltose (mg biomass)⁻¹ h⁻¹. The pattern and levels of α-glucosidase (the enzyme degrading maltose) detected intracellularly in each case, indicate that growth rate effectively controls the rate of feeding of glucose to the cell, and thus catabolite repression. Received: 17 February 1997 / Received revision: 29 April 1997 / Accepted: 11 May 1997     

Structures of Conversion Products Formed from 18β-Glycyrrhetinic Acid by Streptomyces sp. G-20

Dynamic profiles of the rate of O₂ generation from press-injured and inoculated rice leaf slices, versus the time after inoculation, discriminated between the incompatible and compatible combination of blast fungus races with a cultivar. The application of sodium saccharin to rice seedlings via the root system for 6 days changed the compatible to incompatible profile. Even after press- injury and inoculation with the compatible conidia, the leaf application of sodium saccharin enhanced superoxide generation. The application of N-methylsaccharin in a similar manner, however, did not enhance the superoxide generation. Inoculation of press-injured leaves with incompatible conidia in the presence of an aqueous diffusate of the germinating compatible conidia changed the incompatible to compatible profile. The application to press-injured of concanavalin A or a lyophylized preparation from 5 m ammonia extracts of rice leaf homogenate prior to stimulating with a resistance-inducing factor (RIF) from the fungus also enhanced the superoxide generation. The RIF, either from the incompatible or compatible race, gave a quite similar profile of activation upon the generation of the superoxide anion.     

Dynamic behavior of glycerol–glucose co-fermentation for 1,3-propanediol production by <Emphasis Type="Italic">Klebsiella pneumoniae</Emphasis> DSM 2026 under micro-aerobic conditions

Sustained oscillations have been observed in cell growth and glycerol metabolism by Klebsiella pneumoniae during long-term continuous cultivations under anaerobic conditions. However, the oscillation behavior of glucose–glycerol co-fermentation under micro-aerobic conditions has yet not been studied. In this study, the unclear mechanism of oscillation was investigated by using different substrates including glycerol, glucose, and mixtures of glycerol and glucose. A large perturbation of substrate concentration was operated to study the dynamic behavior of continuous fermentation by K. pneumoniae DSM 2026 under micro-aerobic conditions. Oscillations occurred when 80 g of glycerol l⁻¹ was used as single carbon source or co-substrate with 35 g of glucose l⁻¹, whereas no oscillation was observed when glucose was used alone. During the oscillation phases, parameters periodically passed maxima and minima at a relatively constant time interval, and the period of oscillation was 10–16 h. The comparison between glycerol and glucose metabolism revealed that a potential mechanism of oscillation lies in the accumulation of 3-hydroxypropionaldehyde, which is toxic to cell growth.     

Growth-associated production of poly-β-hydroxybutyrate from glucose or alcoholic distillery wastewater by Actinobacillus sp. EL-9

Summary The characteristics of poly--hydroxybutyrate (PHB) production from glucose or alcoholic distillery wastewater by isolated Actinobacillus sp. EL-9 were investigated. PHB production was not dependent on nutrients limitation in Actinobacillus sp. EL-9. The PHB accumulation of Actibobacillus sp. EL-9 followed a growth-associated type where the cell growth and PHB accumulation were carried out simultaneously. The Actinobacillus sp. EL-9 was shown to synthesize and accumulate PHB from alcoholic distillery wastewater during growth. The best growth and PHB production were obtained with enzyme-hydrolyzed alcoholic distillery wastewater.     

Culture medium containing glucose and glycerol as a mixed carbon source improves ε-poly-<Emphasis Type="SmallCaps">l</Emphasis>-lysine production by <Emphasis Type="Italic">Streptomyces</Emphasis> sp. M-Z18

To improve the efficiency of ε-poly-l-lysine (ε-PL) production by Streptomyces sp. M-Z18, batch and fed-batch fermentations with glucose and glycerol (co-fermentations) were performed. The batch fermentations showed that the initial ratio of glucose to glycerol plays an important role in glucose/glycerol co-fermentation. The optimal glucose/glycerol weight ratio was 30/30; this resulted in a maximum ε-PL productivity of 5.26 g/L/d. Glucose and glycerol were consumed synergistically during the co-fermentation process, and the length of time during which the substrate was exhausted was significantly shortened compared with the single carbon source fermentation. Under optimized conditions, fed-batch fermentations with glucose and glycerol as a mixed carbon source achieved maximum ε-PL concentration and productivity values of 35.14 g/L and 4.85 g/L/d, respectively. These values were respectively 1.43- and 1.39-, and 1.17- and 1.16-folds higher than those obtained from fermentations with glucose and glycerol as single carbon sources. The present study is the first to suggest that glucose/glycerol co-fermentation may be an efficient strategy for ε-PL production by Streptomyces sp. M-Z18.     

Effective production of biologically active water-soluble β-1,3-glucan by a coupled system of Agrobacterium sp. and Trichoderma harzianum

Water-soluble β-1,3-glucan (w-glucan) prepared from curdlan is reported to possess various bioactive and medicinal properties. To develop an efficient and cost-effective microbial fermentation method for the direct production of w-glucan, a coupled fermentation system of Agrobacterium sp. and Trichoderma harzianum (CFS-AT) was established. The effects of Tween-80, glucose flow rate, and the use of a dissolved oxygen (DO) control strategy on w-glucan production were assessed. The addition of 10?g?L^?1 Tween-80 to the CFS-AT enhanced w-glucan production, presumably by loosening the curdlan ultrastructure and increasing the efficiency of curdlan hydrolysis. A two-stage glucose and DO control strategy was optimal for w-glucan production. At the T. harzianum cell growth stage, the optimal glucose flow rate and agitation speed were 2.0?g?L^?1 hr^?1 and 600?rpm, respectively, and at the w-glucan production stage, they were 0.5?g?L^?1 hr^?1 and 400?rpm, respectively. W-glucan production reached 17.31?g?L^?1, with a degree of polymerization of 19–25. Furthermore, w-glucan at high concentrations exhibited anti-tumor activity against MCF-7, HepG2, and Hela cancer cells in vitro. This study provides a novel, cost-effective, eco-friendly, and efficient microbial fermentation method for the direct production of biologically active w-glucan.