Hongyan Yang

Selection and characteristics of a switchgrass-colonizing microbial community to produce extracellular cellulases and xylanases.

A microbial community was selected for growth on dried and NaOH-treated switchgrass. During a 14-day liquid cultivation, a 70% loss in dry weight was observed during the first 4 days and after 14 days, the hemicellulose and cellulose in the system were degraded by 73.5% and 67.3%, respectively. The carboxymethyl cellulase (CMCase) and xylanase levels reached 0.21 and 3.75 IU, respectively. The optimal pH for CMCase and xylanase activities was 5 and 6, respectively. The optimal reaction temperature of CMCase and xylanase was 60°C. A library of bacterial and fungal ribosomal gene sequences obtained from the community showed the presence of Achromobacter xylosoxidans and Alcaligenes faecalis and of Fusarium sporotrichioides. To our knowledge, this was the first report on a microbial community selected in the presence of switchgrass to produce extracellular cellulases and xylanases.

Degradation of corn stalk by the composite microbial system of MC1

The composite microbial system of MC1 was used to degrade corn stalk in order to determine properties of the degraded products as well as bacterial composition of MC1. Results indicated that the pH of the fermentation broth was typical of lignocellulose degradation by MC1, decreasing in the early phase and increasing in later stages of the degradation. The microbial biomass peaked on the day 3 after degradation. The MC1 efficiently degraded the corn stalk by nearly 70% during which its cellulose content decreased by 71.2%, hemicellulose by 76.5% and lignin by 24.6%. The content of water-soluble carbohydrates (WSC) in the fermentation broth increased progressively during the first three days, and decreased thereafter, suggesting an accumulation of WSC in the early phase of the degradation process. Total levels of various volatile products peaked in the third day after degradation, and 7 types of volatile products were detected in the fermentation broth. These were ethanol, acetic acid, 1,2-ethanediol, propanoic acid, butanoic acid, 3-methyl-butanoic acid and glycerine. Six major compounds were quantitatively analysed and the contents of each compound were ethanol (0.584 g/L), acetic acid (0.735 g/L), 1,2-ethanediol (0.772 g/L), propanoic acid (0.026 g/L), butanoic acid (0.018 g/L) and glycerine (4.203 g/L). Characterization of bacterial cells collected from the culture solution, based on 16S rDNA PCR-DGGE analysis of DNAs, showed that the composition of bacterial community in MC1 coincided basically with observations from previous studies. This indicated that the structure of MC1 is very stable during degradation of different lignocellulose materials.

Process of rice straw degradation and dynamic trend of pH by the microbial community MC1.

The process of the rice straw degradation in the fermentor with aeration at 290 ml/h was studied. The results of dissolved oxygen (DO) indicated that the optimum DO during cellulose degradation by microbial community MC1 ranged from 0.01 to 0.12 mg/L. The change model of pH values was as follows: irrespective of the initial pH of the medium, pH values decreased rapidly to approximate 6.0 after being inoculated within 48 h when cellulose was strongly degraded, and then increased slowly to 8.0-9.0 until cellulose was degraded completely. During the degradation process, 15 kinds of organic compounds were checked out by GC-MS. Most of them were organic acids. Quantity analysis was carried out, and the maximum content compound was ethyl acetate which reached 13.56 g/L on the day 4. The cellulose degradation quantity and ratio analyses showed that less quantity (under batch fermentation conditions) and longer interval (under semi-fermentation conditions) of rice straw added to fermentation system were contributed to matching the change model of pH, and increasing the quantity and ratio of rice straw degradation during cellulose degrading process. The highest degradation ratio was observed under the condition of rice straw added one time every five days (under semi-fermentation conditions).

Material and microbial changes during corn stalk silage and their effects on methane fermentation.

Silage efficiency is crucial for corn stalk storage in methane production. This study investigated characteristics of dynamic changes in materials and microbes during the silage process of corn stalks from the initial to stable state. We conducted laboratory-scale study of different silage corn stalks, and optimized silage time (0, 2, 5, 10, 20, and 30days) for methane production and the endogenous microbial community. The volatile fatty acid concentration increased to 3.00g/L on Day 10 from 0.42g/L on Day 0, and the pH remained below 4.20 from 5.80. The lactic acid concentration (44%) on Day 10 lowered the pH and inhibited the methane yield, which gradually decreased from 229mL/g TS at the initial state (Day 0, 2) to 207mL/g TS at the stable state (Day 10, 20, 30). Methanosaeta was the predominant archaea in both fresh and silage stalks; however, richness decreased from 14.11% to 4.75%.

Diversity of endophytic fungi from roots of Panax ginseng and their saponin yield capacities.

Endophytes of medicinal plants have the capacity to synthesis same or similar active substances with their hosts. To investigate the diversity and capacity to produce saponins of endophytic fungi of Panax ginseng, thirty-eight strains of were isolated. Polymerase chain reaction (PCR) and sequencing were used to identify the isolates, and saponins concentrations in the cultures were measured. Agar diffusion method was used to test antimicrobial activity. High-performance liquid chromatography (HPLC) was used to analyze ginsenosides produced by representative strains. Nectria, Aspergillus, Fusarium, Verticillium, Engyodontium, Plectosphaerella, Penicillium, Cladosporium, and Ascomycete species were isolated. Overall, 18.4% of the isolates belonged to Nectria (Nectria haematococca), 13.2% belonged to Aspergillus, and 10.5% belonged to Penicillium. The highest concentration of triterpenoid saponin was 0.181 mg/ml (Pg27), followed by 0.144 mg/ml (Pg30 and Pg42-1). According to the results of the phylogenetic results, these isolates were species of Fusarium, Aspergillus and Verticillium, respectively. The culture filtrate of Pg30 exhibited its antibacterial activity Staphylococcus aureus. Pg 27 and Pg30 could excrete the substances to inhibit the growth of Rhizoctonia solani. Pg42-1 showed strong inhibition against Klebsiella pneumoniae. From HPLC results, the ginsenoside Rb2 was detected in both Pg27 and Pg30 cultures. The ginsenoside Rc was found in Pg42-1 cultures. In conclusion, thirty-eight endophytic fungal strains were isolated and Pg27 (Fusarium sp.) has a potential application value in saponins production.

Isolation and Characterization of Saponin-Producing Fungal Endophytes from Aralia elata in Northeast China

The purpose of this study was to investigate the diversity of endophytic fungi of Aralia elata distributed in Northeast China as well as their capacity to produce saponins. Ninety-six strains of endophytic fungi were isolated, and polymerase chain reaction (PCR) and sequencing were employed to identify the isolates. The saponin concentrations of the culture filtrates of representative strains were measured. The agar diffusion method was used to test antimicrobial activity, while high-performance liquid chromatography (HPLC) was employed to identify the saponins produced by representative strains. Alternaria, Botryosphaeria, Camarosporium, Cryptosporiopsis, Diaporthe, Dictyochaeta, Penicillium, Fusarium, Nectria, Peniophora, Schizophyllum, Cladosporium and Trichoderma species were isolated in this study. Overall, 25% of the isolates belonged to Diaporthe (Diaporthe eres), and 12.5% belonged to Alternaria. The highest concentration of saponins was produced by G22 (2.049 mg/mL). According to the results of the phylogenetic analysis, G22 belonged to the genus Penicillium. The culture filtrate of G22 exhibited antibacterial activity against Staphylococcus aureus, and ginsenosides Re and Rb2 were detected in G22 culture filtrates by HPLC.

Effects of Lactobacillus curvatus and Leuconostoc mesenteroides on suan cai fermentation in Northeast China.

To investigate the effects of Lactobacillus curvatus and Leuconostoc mesenteroides on suan cai (pickled Chinese cabbage) fermentation, L. curvatus and/or Ln. mesenteroides were inoculated into suan cai. Physicochemical indexes were measured, and the microbial dynamics during the fermentation were analyzed by Illumina MiSeq sequencing and quantitative polymerase chain reaction (qPCR). The results showed that inoculation with lactic acid bacteria (LAB) lowered the pH of the fermentation system more rapidly. The decrease in water-soluble carbohydrates in the inoculated treatments occurred more rapidly than in the control. The LAB counts in the control were lower than in other inoculated treatments during the first 12 days of fermentation. According to the Illumina MiSeq sequencing analyses, Firmicutes, Proteobacteria, Bacteroidetes, Actinobacteria, Cyanobacteria, Fusobacteria, and Verrucomicrobia were present in the fermentations, along with other unclassified bacteria. Generally, Firmicutes was predominant during the fermentation in all treatments. At the genus level, 16 genera were detected. The relative abundance of Lactobacillus in all inoculated treatments was higher than in the control. The relative abundance of Lactobacillus in the treatments containing L. curvatus was higher than in the Ln. mesenteroides-only treatment. The relative abundance of Leuconostoc in the Ln. mesenteroides-containing treatments increased continuously throughout the fermentation. Leuconostoc was highest in the Ln. mesenteroides-only treatment. According to the qPCR results, L. curvatus and/or Ln. mesenteroides inoculations could effectively inhabit the fermentation system. L. curvatus dominated the fermentation in the inoculated treatments.

Effects of cultivation conditions on the diversity of microbes involved in the conversion of rice straw to fodder

To confirm the optimum cultivation conditions for analyzing lactic acid bacterial communities and to provide the cultivation foundation for lactic acid bacterial communities that were used to convert straw into fodder, fermented rice straw was inoculated into 13 different broths. After 48 h of cultivation, pH values, volatile products, and microbial diversity were analyzed. Except for LAB broth, the pH values of the other broths could decrease to approximately 4.5. GC/MS analysis showed that lactic acid in Tomato MRS broth, MRS broth, LAB broth, and Tomato juice broth was higher than that in the other broths. DNA concentration analysis showed that the counts of microbes in Tomato MRS broth were 2.5 times of those in other broths and that tomato juice favored the reproduction of the microbes. Denaturing gradient gel electrophoresis (DGGE) analysis showed that the number of lactic acid bacterial species in HYA broth, Tomato juice broth, and Tomato MRS broth were higher than those in the other broths.