Process engineering aspects of the production of cephalosporin C by Acremonium chrysogenum. Part II. Cultivation in diluted and enriched complex media

Harnessing Nature's Anaerobes for Biotechnology and Bioprocessing

Industrial biotechnology has the potential to decrease our reliance on petroleum for fuel and bio-based chemical production and also enable valorization of waste streams. Anaerobic microorganisms thrive in resource-limited environments and offer an array of novel bioactivities in this regard that could revolutionize biomanufacturing. However, they have not been adopted for widespread industrial use owing to their strict growth requirements, limited number of available strains, difficulty in scale-up, and genetic intractability. This review provides an overview of current and future uses for anaerobes in biotechnology and bioprocessing in the postgenomic era. We focus on the recently characterized anaerobic fungi (Neocallimastigomycota) native to the digestive tract of large herbivores, which possess a trove of enzymes, pathways, transporters, and other biomolecules that can be harnessed for numerous biotechnological applications. Resolving current genetic intractability, scale-up, and cultivation challenges will unlock the potential of these lignocellulolytic fungi and other nonmodel micro-organisms to accelerate bio-based production.

Involvement of nitrogen-containing compounds in beta-lactam biosynthesis and its control

Biosynthesis of beta-lactam antibiotics by fungi and actinomycetes is markedly affected by compounds containing nitrogen. The different processes employed by the spectrum of microbes capable of making these valuable compounds are affected differently by particular compounds. Ammonium ions, except at very low concentrations, exert negative effects via nitrogen metabolite repression, sometimes involving the nitrogen regulatory gene nre. Certain amino acids are precursors or inducers, whereas others are involved in repression and, in certain cases, as inhibitors of biosynthetic enzymes and of enzymes supplying precursors. The most important amino acids from the viewpoint of regulation are lysine, methionine, glutamate and valine. Surprisingly, diamines such as diaminopropane, putrescine and cadaverine induce cephamycin production by actinomycetes. In addition to penicillins and cephalosporins made by fungi and cephamycins made by actinomycetes, other beta-lactams are made by actinomycetes and unicellular bacteria. These include clavams (e.g., clavulanic acid), carbapenems (e.g., thienamycin), nocardicins and monobactams. Here also, amino acids are precursors and inhibitors, but only little is known about regulation. In the case of the simplest carbapenem made by unicellular bacteria, i.e., 1-carba-2-em-3-carboxylic acid, quorum sensors containing homoserine lactone are inducers.

Morphologically structured model for antitumoral retamycin production during batch and fed-batch cultivations ofStreptomyces olindensis

A morphologically structured model is proposed to describe trends in biomass growth, substrate consumption, and antitumoral retamycin production during batch and fed-batch cultivations of Streptomyces olindensis. Filamentous biomass is structured into three morphological compartments (apical, subapical, and hyphal), and the production of retamycin, a secondary metabolite, is assumed to take place in the subapical cell compartment. Model accounts for the effect of glucose as well as complex nitrogen source on both the biomass growth and retamycin production. Laboratory data from bench-scale batch and fed-batch fermentations were used to estimate some model parameters by nonlinear regression. The predictive capability of the model was then tested for additional fed-batch and continuous experiments not used in the previous fitting procedure. The model predictions show fair agreement to the experimental data. The proposed model can be useful for further studies on process optimization and control.