Sucrose fed-batch strategy enhanced biomass, polysaccharide, and ganoderic acids production in fermentation of Ganoderma lucidum 5.26.

Ganoderma, as a Chinese traditional medicine, has multiple bioactivities. However, industrial production was limited due to low yield during Ganoderma fermentation. In this work, sucrose was found to greatly enhance intracellular polysaccharide (IPS) content and specific extracellular polysaccharide (EPS) production rate. The mechanism was studied by analyzing the activities of enzymes related to polysaccharide biosynthesis. The results revealed that sucrose regulated the activities of phosphoglucomutase and phosphoglucose isomerase. When glucose and sucrose mixture was used as carbon source, biomass, polysaccharide and ganoderic acids (GAs) production was greatly enhanced. A sucrose fed-batch strategy was developed in 10-L bioreactor, and was scaled up to 300-L bioreactor. The biomass, EPS and IPS production was 25.5, 2.9 and 4.8 g/L, respectively, which was the highest biomass and IPS production in pilot scale. This study provides information for further understanding the regulation mechanism of Ganoderma polysaccharide biosynthesis. It demonstrates that sucrose fed-batch is a useful strategy for enhancing Ganoderma biomass, polysaccharide and GAs production.

Patterns of change in the population and spatial distribution of oriental white storks (Ciconia boyciana) wintering in Poyang Lake.

Using total counts in simultaneous annual surveys, we monitored the population size and spatial distribution of oriental white storks (Ciconia boyciana) wintering in Poyang Lake between 1998 and 2011. Results showed that Poyang Lake wetland is an important wintering ground for oriental white storks, with an annual average population number of 2 305±326. The population sizes in 2004, 2005, 2010, and 2011 were higher than the highest-ever estimate of its global population. In 2005, we recorded 3 789 individuals, which was the maximum population number within the period of 1998-2011. The storks inhabited 52 lakes, with the greatest distance between these lakes being 180.3 km. The storks presented a clustered distribution pattern in the Poyang Lake wetland, irrespective of the number of individuals or occurrence frequencies. Shahu, Dahuchi, Banghu, and Hanchihu were most frequently used lakes and had the largest annual average numbers of storks. There was a significant positive correlation between occurrence frequency and annual average number of storks in the lakes. Most of the lakes important for storks were covered by existing nature reserves, though some lakes outside the reserves were also frequently used. About 64.9%±5.5% of the storks were found in nature reserves. In addition, the storks more frequently used and clumped in significantly larger flocks in lakes within nature reserves than lakes outside.

Screening of Ganoderma strains with high polysaccharides and ganoderic acid contents and optimization of the fermentation medium by statistical methods.

Polysaccharides and ganoderic acids (GAs) are the major bioactive constituents of Ganoderma species. However, the commercialization of their production was limited by low yield in the submerged culture of Ganoderma despite improvement made in recent years. In this work, twelve Ganoderma strains were screened to efficiently produce polysaccharides and GAs, and Ganoderma lucidum 5.26 (GL 5.26) that had been never reported in fermentation process was found to be most efficient among the tested stains. Then, the fermentation medium was optimized for GL 5.26 by statistical method. Firstly, glucose and yeast extract were found to be the optimum carbon source and nitrogen source according to the single-factor tests. Ferric sulfate was found to have significant effect on GL 5.26 biomass production according to the results of Plackett-Burman design. The concentrations of glucose, yeast extract and ferric sulfate were further optimized by response surface methodology. The optimum medium composition was 55 g/L of glucose, 14 g/L of yeast extract, 0.3 g/L of ferric acid, with other medium components unchanged. The optimized medium was testified in the 10-L bioreactor, and the production of biomass, IPS, total GAs and GA-T enhanced by 85, 27, 49 and 93 %, respectively, compared to the initial medium. The fermentation process was scaled up to 300-L bioreactor; it showed good IPS (3.6 g/L) and GAs (670 mg/L) production. The biomass was 23.9 g/L in 300-L bioreactor, which was the highest biomass production in pilot scale. According to this study, the strain GL 5.26 showed good fermentation property by optimizing the medium. It might be a candidate industrial strain by further process optimization and scale-up study.

Temperature shift-induced reactive oxygen species enhanced validamycin A production in fermentation of Streptomyces hygroscopicus 5008.

In order to enhance the production of validamycin A (VAL-A), a widely used agricultural antibiotic, a temperature shift strategy was developed in the fermentation of Streptomyces hygroscopicus 5008. VAL-A production and the transcriptional levels of its structural genes were enhanced in the optimal temperature shift condition. The addition of diphenyleneiodonium [DPI, reactive oxygen species (ROS) inhibitor] inhibited intracellular ROS level and VAL-A production, which indicated that ROS signal might contribute to the enhancement of VAL-A production in the temperature shift process. The transcriptional levels of stress response sigma factors SigmaB and SigmaH as well as global regulator PhoRP were enhanced, which suggested that these regulators might participate in the signal pathway. This study developed a useful strategy for VAL-A production. It will help to further understand the regulation mechanism of ROS on VAL-A synthesis. The involvement of ROS in this process will encourage researchers to develop new ROS induction strategies to enhance VAL-A production.

Impact of nitrogen concentration on validamycin A production and related gene transcription in fermentation of Streptomyces hygroscopicus 5008.

Validamycin A (VAL-A) is an important and widely used agricultural antibiotic. In this study, statistical screening designs were applied to identify significant medium variables for VAL-A production and to find their optimal levels. The optimized medium caused 70% enhancement of VAL-A production. The difference between optimized medium and original medium suggested that low nitrogen source level might attribute to the enhancement of VAL-A production. The addition of different nitrogen sources to the optimized medium inhibited VAL-A production, which confirmed the importance of nitrogen concentration for VAL-A production. Furthermore, differences in structural gene transcription and enzyme activity between the two media were assayed. The results showed that lower nitrogen level in the optimized medium could regulate VAL-A production in gene transcriptional level. Our previous study indicated that the transcription of VAL-A structural genes could be enhanced at elevated temperature. In this work, the increased fermentation temperature from 37 to 42 °C with the optimized medium enhanced VAL-A production by 39%, which testified to the importance of structural gene transcription in VAL-A production. The information is useful for further VAL-A production enhancement.

Enhanced production of validamycin A by H2O2-induced reactive oxygen species in fermentation of Streptomyces hygroscopicus 5008.

A novel fermentation strategy to enhance antibiotics production was demonstrated by inducing reactive oxygen species (ROS), and validamycin A (VAL-A) production by Streptomyces hygroscopicus 5008 in agro-industrial residues containing medium was taken as an example. By optimizing H2O2 amount and addition time, the intracellular ROS level was increased, and VAL-A production titer was enhanced by 40% on day 4 when 25 µM H2O2 was added at 8th h of fermentation. Addition of diphenyleneiodonium chloride (ROS inhibitor) reduced the H2O2 induction effect. The transcription level of eight VAL-A structure genes was enhanced by ROS, and activities of glucose-6-phosphate dehydrogenase and ValG enzyme were increased while glyceraldehyde 3-phosphate dehydrogenase activity was inhibited. This work demonstrated that ROS induction was a useful strategy for VAL-A fermentation, and the information on gene transcription and enzyme activities may be helpful to further understanding the mechanism of ROS effect on the antibiotic biosynthesis.

Effect of fermentation temperature on validamycin A production by Streptomyces hygroscopicus 5008.

Validamycin A (VAL-A), produced by Streptomyces hygroscopicus, is an important anti-fungal agro-antibiotic. In this work, the effect of fermentation temperature on VAL-A biosynthesis by S. hygroscopicus 5008 was investigated between 28 degrees C and 42 degrees C, and an interesting threshold of temperature for VAL-A biosynthesis was found between 35 degrees C and 37 degrees C. At a relatively higher temperature, a much higher VAL-A productivity was obtained together with faster protein synthesis and sugar consumption. Transcriptional analysis of samples from early, middle and late stages of fermentation at various temperatures demonstrated that three operons, valABC, valKLMN and valG, for all eight necessary structure genes, were dramatically promoted when temperature reached the threshold. Activities of both glucose-6-phosphate dehydrogenase (G6PDH) of pentose-phosphate pathway and ValG of VAL-A biosynthesis were also enhanced at a higher cultivation temperature. The interesting temperature effect with a 2 degrees C threshold shift from 35 degrees C to 37 degrees C on the antibiotic biosynthesis was understood to be related to the gene transcriptional levels and key enzyme activities.