Transcriptome analysis of Rhizopus oryzae seed pellet formation using triethanolamine

Rhizopus oryzae (R. oryzae) can effectively produce organic acids, and its pellet formation in seed cultures has been shown to significantly enhance subsequent fermentation processes. Despite advances in strain development, simple and effective methods for inducing pellet morphology and a basic understanding of the mechanisms controlling this process could facilitate substantial increases in efficiency and product output. Here, we report that 1.5% triethanolamine (TEOA) in seed culture medium can activate the growth of R. oryzae spores in compact and uniform pellets which is optimal for fermentation conditions. Analysis of fermentation kinetics showed that the production of fumaric and L-malic acid increases 293% and 177%, respectively. Transcriptomic analysis revealed that exposure of R. oryzae to 1.5% TEOA during the seed culture activated the phosphatidylinositol and mitogen-activated protein kinase signaling pathways. Theses pathways subsequently stimulated the downstream carbohydrate-active synthases and hydrolases that required for cell wall component synthesis and reconstruction. Our results thus provide insight into the regulatory pathways controlling pellet morphology germane to the viability of seed cultures, and provide valuable reference data for subsequent optimization of organic acid fermentation by R. oryzae.

Chemical composition and physical properties of coffee (Coffea robusta) bee pollen in Daklak province, Vietnam

The main purpose of this study was to determine the chemical composition of monofloral bee-collected pollen from the coffee (Coffea robusta) plant and its pellet morphology. According to the results coffee bee pollen (CBP) has a high nutritional value. It contains a large percentage of protein, reducing sugar, and lipid. Also, vitamins (B2 and E) and minerals (K, Ca, and P) were found in CBP. In addition, the results revealed that the total polyphenols content (TPC) was 10.62 mg GAE/g dry weight (DW) and antioxidant activity (AA) of CBP was 5.52 μmol TE/g DW. Some physical properties of CBP pellet were recorded such as moisture, relative diameter, sphericity, bulk density, and colour parameters. The pollen pellet exhibits shapes of colour from light to dark yellow. These results pointed out that CBP can be used as a remarkable source of compounds with antioxidant activity and health-protective capacity for humans.

Effects of nitrogen from different sources on mycelial biomass and polysaccharide production and pellet morphology in submerged cultures of Grifola frondosa

The effects of nitrogen in the medium on the production of mycelial biomass, extracellular polysaccharides (EPS), and intracellular polysaccharides (IPS) was investigated in submerged cultures of Grifola frondosa. In addition, the effects on pellet morphology were examined. The maximum production levels of mycelial biomass (2.32 g/L), EPS (1.58 g/L), and IPS (29.1 mg/L) were obtained when the nitrogen sources in the medium were yeast extract, malt extract, and peptone, respectively. Using yeast extract as the nitrogen source yielded the maximum mycelial biomass, and morphological characterization revealed a composition of 47% large pellets (fraction L), 20% small pellets (fraction S), and 33% adhesive mycelia (fraction A). The maximum circularity value and the minimum roughness value of the pellets were observed using yeast extract cultures. Both the compactness (0.53) and circularity (0.15) of the pellets were the lowest among the seven types of nitrogen sources, but the roughness (2.86) was the highest in malt extract, which was the nitrogen source that resulted in maximum polysaccharide production. The results revealed that the production levels of mycelial biomass, EPS, and IPS of G. frondosa were associated with changes in pellet morphology due to the source of nitrogen in the medium.

Evidence that Bacteria Packaging by Tetrahymena Is a Widespread Phenomenon

Protozoa are natural predators of bacteria, but some bacteria can evade digestion once phagocytosed. Some of these resistant bacteria can be packaged in the fecal pellets produced by protozoa, protecting them from physical stresses and biocides. Depending on the bacteria and protozoa involved in the packaging process, pellets can have different morphologies. In the present descriptive study, we evaluated the packaging process with 20 bacteria that have never been tested before for packaging by ciliates. These bacteria have various characteristics (shape, size, Gram staining). All of them appear to be included in pellets produced by the ciliates Tetrahymena pyriformis and/or T. thermophila in at least one condition tested. We then focused on the packaging morphology of four of these bacteria. Our results demonstrated that, as shown previously for Mycobacterium smegmatis, the packaging of Microbacterium oxydans, Micrococcus luteus, and Cupriavidus sp. was formed of a single layer of material. The packaging of Cellulosimicrobiumfunkei was made of indistinguishable material. A different pellet morphology was obtained for each of the four bacterial strains studied. The ingestion of small bacteria resulted in rounder, denser, and more regular pellets. These results support the idea that bacteria packaging is a relatively widespread phenomenon.

Characterization and mechanism of lead and zinc biosorption by growing Verticillium insectorum J3

Verticillium insectorum J3 was isolated from a local lead-zinc deposit tailing, and its biosorption characteristics and reaction to the toxicities of different Pb(II) and Zn(II) concentrations were investigated. SEM, FTIR, a pH test and a desorption experiment were carried out to identify a possible mechanism. The biosorption of J3 presented an inhibition trend at low concentrations (25-75 mg L-1) and promotion at high concentrations (100-300 mg L-1). J3 absorbed Pb(II) prior to Zn(II) and produced alkaline substances, while mycelial and pellet morphology modifications were important for the removal of Pb(II) and Zn(II) under different stressful conditions (SEM results). Both intracellular accumulation and extracellular absorption may contribute to the removal of Pb(II) at lower concentrations (25-50 mg L-1), although mainly extracellular biosorption occurred at higher concentrations (75-300 mg L-1). However, Zn(II) bioaccumulation occurred at all concentrations assayed. Verticillium insectorum J3 may have evolved active defenses to alleviate the toxicity of heavy metals and proved to be a highly efficient biosorbent, especially for Pb(II) at high concentrations. This study is a useful reference for the development of biotreatment technologies to mitigate heavy metal waste.