Fundamental features of microbial cellulose utilization are examined at successively higher levels of aggregation encompassing the structure and composition of cellulosic biomass, taxonomic diversity, cellulase enzyme systems, molecular biology of cellulase enzymes, physiology of cellulolytic microorganisms, ecological aspects of cellulase-degrading communities, and rate-limiting factors in nature. The methodological basis for studying microbial cellulose utilization is considered relative to quantification of cells and enzymes in the presence of solid substrates as well as apparatus and analysis for cellulose-grown continuous cultures. Quantitative description of cellulose hydrolysis is addressed with respect to adsorption of cellulase enzymes, rates of enzymatic hydrolysis, bioenergetics of microbial cellulose utilization, kinetics of microbial cellulose utilization, and contrasting features compared to soluble substrate kinetics. A biological perspective on processing cellulosic biomass is presented, including features of pretreated substrates and alternative process configurations. Organism development is considered for "consolidated bioprocessing" (CBP), in which the production of cellulolytic enzymes, hydrolysis of biomass, and fermentation of resulting sugars to desired products occur in one step. Two organism development strategies for CBP are examined: (i) improve product yield and tolerance in microorganisms able to utilize cellulose, or (ii) express a heterologous system for cellulose hydrolysis and utilization in microorganisms that exhibit high product yield and tolerance. A concluding discussion identifies unresolved issues pertaining to microbial cellulose utilization, suggests approaches by which such issues might be resolved, and contrasts a microbially oriented cellulose hydrolysis paradigm to the more conventional enzymatically oriented paradigm in both fundamental and applied contexts.

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Microbial cellulose utilization: fundamentals and biotechnology.

Antibiotics have always been considered one of the wonder discoveries of the 20th century. This is true, but the real wonder is the rise of antibiotic resistance in hospitals, communities, and the environment concomitant with their use. The extraordinary genetic capacities of microbes have benefitted from man's overuse of antibiotics to exploit every source of resistance genes and every means of horizontal gene transmission to develop multiple mechanisms of resistance for each and every antibiotic introduced into practice clinically, agriculturally, or otherwise. This review presents the salient aspects of antibiotic resistance development over the past half-century, with the oft-restated conclusion that it is time to act. To achieve complete restitution of therapeutic applications of antibiotics, there is a need for more information on the role of environmental microbiomes in the rise of antibiotic resistance. In particular, creative approaches to the discovery of novel antibiotics and their expedited and controlled introduction to therapy are obligatory.

Origins and Evolution of Antibiotic Resistance

SUMMARY A collection of 267 strains, representing many of the principal biotypes among aerobic pseudomonads, has been subjected to detailed study, with particular emphasis on biochemical, physiological and nutritional characters. A total of 146 different organic compounds were tested for their ability to serve as sources of carbon and energy. Other characters that were studied included : production of extracellular hydrolases; nitrogen sources and growth factor requirements H-chemolithotrophy; denitrifying ability; pigment production; ability to accumulate poly-p-hydroxybutyrate as a cellular reserve material; biochemical mechanisms of aromatic ring cleavage; and nature of the aerobic electron transport system. The resultant data have revealed many hitherto unrecognized characters of taxonomic significance. As a consequence, it has become possible to recognize among the biotypes examined a limited number of species which can be readily and clearly distinguished from one another by multiple, unrelated phenotypic differences.

The Aerobic Pseudomonads a Taxonomic Study

The short history, specific features and future prospects of research of microbial metabolites, including antibiotics and other bioactive metabolites, are summarized. The microbial origin, diversity of producing species, functions and various bioactivities of metabolites, unique features of their chemical structures are discussed, mainly on the basis of statistical data. The possible numbers of metabolites may be discovered in the future, the problems of dereplication of newly isolated compounds as well as the new trends and prospects of the research are also discussed.

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Bioactive microbial metabolites.

The use of fossil fuels is now widely accepted as unsustainable due to depleting resources and the accumulation of greenhouse gases in the environment that have already exceeded the “dangerously high” threshold of 450 ppm CO2-e. To achieve environmental and economic sustainability, fuel production processes are required that are not only renewable, but also capable of sequestering atmospheric CO2. Currently, nearly all renewable energy sources (e.g. hydroelectric, solar, wind, tidal, geothermal) target the electricity market, while fuels make up a much larger share of the global energy demand (∼66%). Biofuels are therefore rapidly being developed. Second generation microalgal systems have the advantage that they can produce a wide range of feedstocks for the production of biodiesel, bioethanol, biomethane and biohydrogen. Biodiesel is currently produced from oil synthesized by conventional fuel crops that harvest the sun’s energy and store it as chemical energy. This presents a route for renewable and carbon-neutral fuel production. However, current supplies from oil crops and animal fats account for only approximately 0.3% of the current demand for transport fuels. Increasing biofuel production on arable land could have severe consequences for global food supply. In contrast, producing biodiesel from algae is widely regarded as one of the most efficient ways of generating biofuels and also appears to represent the only current renewable source of oil that could meet the global demand for transport fuels. The main advantages of second generation microalgal systems are that they: (1) Have a higher photon conversion efficiency (as evidenced by increased biomass yields per hectare): (2) Can be harvested batch-wise nearly all-year-round, providing a reliable and continuous supply of oil: (3) Can utilize salt and waste water streams, thereby greatly reducing freshwater use: (4) Can couple CO2-neutral fuel production with CO2 sequestration: (5) Produce non-toxic and highly biodegradable biofuels. Current limitations exist mainly in the harvesting process and in the supply of CO2 for high efficiency production. This review provides a brief overview of second generation biodiesel production systems using microalgae.

https://www.springer.com/cda/content/document/cda_downloaddocument/BioEnergyResearch_Second+Generation+Biofuels+High-Efficiency+Microalgae+for+Biodiesel+Production.pdf?SGWID=0-0-45-1347846-0

Second generation biofuels: high-efficiency microalgae for biodiesel production

Control ofAntibiotic Biosynthesis

Dithiothreitol reactivates desacetoxycephalosporin C synthetase after inactivation

A vigorous debate on gradual substitution of petroleum by use of renewable alternatives such as starch or sugar to ethanol or cellulosic biofuels dominates the political and economic agenda worldwide. Ethanol has been produced from sugarcane since the 1990s; an aggressive program has achieved the use of neat ethanol in new cars. There are various reports on lignocellulosic ethanol production using biomass. These indicate that ethanol from lignocellulosic biomass reduces “greenhouse gases” (GHG) emissions by about 80% compared to gasoline, whereas ethanol from corn reduces them by 20 to 30%. The cellulase system in Clostridia thermocellum comprises multiple enzyme complexes. In the case of hemicellulose, enzymatic saccharification by C. thermocellum occurs, generating xylose and xylobiose; both are utilized by Thermoanaerobacterium saccharolyticum for production of ethanol, lactic acid, and acetic acid. The combination of both microorganisms in the production of ethanol has been central in the development of the consolidated bioprocessing concept of researchers. Although the coculture system is very promising, several barriers exist such as end product inhibition by the produced ethanol. This disadvantage can almost be counterbalanced by the process of ethanol distillation from dilute broths. The work by researchers on the structure of the cell surface multisubunit complex called the cellulosome has been very important for understanding the detailed interactions between the organism and its enzymes and the binding affinity to cellulose through the cellulosic binding domain.

Ethanol, Biomass, and Clostridia

The carbon and nitrogen source requirements of Aspergillus fumigatus NRRL 2436 for growth and production of the angiogenesis inhibitor fumagillin were studied in chemically defined media. Both carbon and nitrogen sources strongly influenced fumagillin formation. Two out of 29 carbon sources tested interfered with fumagillin biosynthesis. The best combination of two carbon sources was 30 g L−1 xylan and 50 g L−1 mannose. Of fifteen nitrogen sources tested, three ammonium salts (chloride, sulfate, and dibasic phosphate) failed to support fumagillin formation, presumably due to the low pH which developed. The dosage-response study of the best nitrogen source, L-glutamic acid, revealed that 9 g L−1 was optimal. Volumetric production of fumagillin was increased by 15-fold over that in the starting (Peterson-Goldstein) medium as a result of these findings.

Carbon and nitrogen source nutrition of fumagillin biosynthesis by Aspergillus fumigatus.

Antibodies raised against the SL subunit of theClostridium thermocellum cellulosome were used to screen a library ofC. thermocellum chromosomal DNA fragments constructed in the vector λgt11. A DNA fragment that encoded a polypeptide that crossreacted with the anti-SL antibodies was isolated and its restriction map elucidated. No similarity with other previously cloned DNA fragments has been found. The anti-SL, crossreacting polypeptide was isolated from recombinantEscherichia coli and found to have a mol mass of 37,000 Da and to possess low levels of CMCase and Avicelase activity. Using CMC as the substrate, a temperature optimum of 55°C and a pH optimum of 6.6 were observed. These properties were compared to those ofC. thermocellum SL isolated by electroelution from an SDS gel, which was also found to possess low levels of CMCase and Avicelase activities. In addition, the SL proteins produced inC. thermocellum andE. coli were able to interact positively against Avicel with an endoglucanase (SS) purified from theC. thermocellum crude cellulase preparation, and with a recombinant protein that crossreacted with anti-SS antibodies.

Arnold L. Demain

Papers

Control ofAntibiotic Biosynthesis

Dithiothreitol reactivates desacetoxycephalosporin C synthetase after inactivation

Ethanol, Biomass, and Clostridia

Carbon and nitrogen source nutrition of fumagillin biosynthesis by Aspergillus fumigatus.

Cloning and expression of a Clostridium thermocellum DNA fragment that encodes a protein related to cellulosome component SL.