Statistical method for testing the neutral mutation hypothesis by DNA polymorphism.

Application of solid-state fermentation to food industry—A review

Biotechnological potential of coffee pulp and coffee husk for bioprocesses

https://pubs.rsc.org/en/content/articlepdf/2020/gc/d0gc01647k

Review of recent advances in the biodegradability of polyhydroxyalkanoate (PHA) bioplastics and their composites

Microbial secondary metabolites are low molecular mass products, not essential for growth of the producing cultures, but very important for human health. They include antibiotics, antitumor agents, cholesterol-lowering drugs, and others. They have unusual structures and are usually formed during the late growth phase of the producing microorganisms. Its synthesis can be influenced greatly by manipulating the type and concentration of the nutrients formulating the culture media. Among these nutrients, the effect of the carbon sources has been the subject of continuous studies for both, industry and research groups. Different mechanisms have been described in bacteria and fungi to explain the negative carbon catabolite effects on secondary metabolite production. Their knowledge and manipulation have been useful either for setting fermentation conditions or for strain improvement. During the last years, important advances have been reported on these mechanisms at the biochemical and molecular levels. The aim of the present review is to describe these advances, giving special emphasis to those reported for the genus Streptomyces.

Production of microbial secondary metabolites: Regulation by the carbon source

Acidobacteria represents an underrepresented soil bacterial phylum whose members are pervasive and copiously distributed across nearly all ecosystems. Acidobacterial sequences are abundant in soils and represent a significant fraction of soil microbial community. Being recalcitrant and difficult-to-cultivate under laboratory conditions, holistic, polyphasic approaches are required to study these refractive bacteria extensively. Acidobacteria possesses an inventory of genes involved in diverse metabolic pathways, as evidenced by their pan-genomic profiles. Because of their preponderance and ubiquity in the soil, speculations have been made regarding their dynamic roles in vital ecological processes viz., regulation of biogeochemical cycles, decomposition of biopolymers, exopolysaccharide secretion, and plant growth promotion. These bacteria are expected to have genes that might help in survival and competitive colonization in the rhizosphere, leading to the establishment of beneficial relationships with plants. Exploration of these genetic attributes and more in-depth insights into the belowground mechanics and dynamics would lead to a better understanding of the functions and ecological significance of this enigmatic phylum in the soil-plant environment. This review is an effort to provide a recent update into the diversity of genes in Acidobacteria useful for characterization, understanding ecological roles, and future biotechnological perspectives.

/pdf/recent-understanding-of-soil-acidobacteria-and-their-1ei9779cwo.pdf

Recent Understanding of Soil Acidobacteria and Their Ecological Significance: A Critical Review.

Publisher Summary This chapter reviews the process characteristics of fungal growth in submerged cultures and its relationship to the kinetics of product formation with a focus on the unique growth morphology of filamentous fungi in submerged cultures. It discusses the factors affecting fungal morphology and their effects on fungal fermentation and the immobilization of fungal cells and its benefits. Finally, the future of and challenges in using filamentous fungi as biofactories of recombinant proteins are briefly elaborated. Filamentous fungal cells are major biofactories of the past, the present, and the future. The relationship between the cytology of hyphal growth and protein excretion in filamentous fungi has long been observed and reported. The morphological growth forms of filamentous organisms in aerobic submerged cultivation may lead to suspension characteristics quite different from those of bacterial and yeast cultures. In the case of enzyme production, the macro-morphological features of fungi not only affect enzyme production and excretion but also have a significant effect on productivity. The use of immobilized cells in bioprocesses has many advantages over using them in their free forms. Immobilization allows easier separation of cells from the fermentation broth, facilitates the isolation and refinement of products, and allows for the repeated use of cells.

Filamentous Fungal Cultures – Process Characteristics, Products, and Applications

The effects of certain nutrients on natamycin production by Streptomyces natalensis in submerged batch culture were studied. The production of this antibiotic required glucose in the cultivation medium with a concentration of 20 g/l. On the other hand, the highest antibiotic production was obtained in a cultivation medium containing 0.05 g/l of potassium dihydrogen phosphate. Further increase in phosphate concentration resulted in a significant increase in biomass concomitant with lower antibiotic production. Among different N-sources tested, only ammonium sulphate, sodium nitrate and beef extract were the suitable nitrogen sources in supporting the antibiotic production. Furthermore, a mixture of beef extract and yeast extract (8 g/l and 2 g/l, respectively) exhibited a synergistic effect in enhancing the natamycin production reaching about 1.5 g/l.

Optimization of the cultivation medium for natamycin production by Streptomyces natalensis.

Agitation effects on morphology and protein productive fractions of filamentous and pelleted growth forms of recombinant Aspergillus niger

This study demonstrates the effect of cultivation conditions on the production of natamycin. Of these conditions, the effect of oxygen limitation and type of inoculum were extensively investigated. Increasing the shaking speed and decreasing the medium volume improved both the volumetric and specific natamycin production. Also, decreasing the dissolved oxygen level in the cultivation medium through the addition of soluble biopolymer (alginate) resulted in a significant decrease in the natamycin yield without effect on the cell growth. On the other hand, spore inoculum yielded higher concentration of natamycin compared to the vegetative cells by about 40%. The maximal cell productivity based on biomass [Yp/x] of about 0.4 [g/g] was obtained by using shake flask of 50 ml working volume agitated at 200 rpm and the inoculum was in the form of spore 2 x 10(8) spores/ml. These results showed that the production process of natamycin is highly dependent on oxygen level in the cultivation medium and type of inoculum as well.

Hesham A. El-Enshasy

Papers

Recent Understanding of Soil Acidobacteria and Their Ecological Significance: A Critical Review.

Filamentous Fungal Cultures – Process Characteristics, Products, and Applications

Optimization of the cultivation medium for natamycin production by Streptomyces natalensis.

Agitation effects on morphology and protein productive fractions of filamentous and pelleted growth forms of recombinant Aspergillus niger

Influence of inoculum type and cultivation conditions on natamycin production by Streptomyces natalensis