Three structural classes of (1-->3)-beta-D-glucans are encountered in some important soil-dwelling, plant-associated or human pathogenic bacteria. Linear (1-->3)-beta-glucans and side-chain-branched (1-->3,1-->2)-beta-glucans are major constituents of capsular materials, with roles in bacterial aggregation, virulence and carbohydrate storage. Cyclic (1-->3,1-->6)-beta-glucans are predominantly periplasmic, serving in osmotic adaptation. Curdlan, the linear (1-->3)-beta-glucan from Agrobacterium, has unique rheological and thermal gelling properties, with applications in the food industry and other sectors. This review includes information on the structure, properties and molecular genetics of the bacterial (1-->3)-beta-glucans, together with an overview of the physiology and biotechnology of curdlan production and applications of this biopolymer and its derivatives.

Curdlan and other bacterial (1→3)-β-d-glucans

While many kinetic models have been developed for the enzymatic hydrolysis of cellulose, few have been extensively applied for process design, optimization, or control. High-solids operation of the enzymatic hydrolysis of lignocellulose is motivated by both its operation decreasing capital costs and increasing product concentration and hence separation costs. This work utilizes both insights obtained from experimental work and kinetic modeling to develop an optimization strategy for cellulose saccharification at insoluble solids levels greater than 15% (w/w), where mixing in stirred tank reactors (STRs) becomes problematic. A previously developed model for batch enzymatic hydrolysis of cellulose was modified to consider the effects of feeding in the context of fed-batch operation. By solving the set of model differential equations, a feeding profile was developed to maintain the insoluble solids concentration at a constant or manageable level throughout the course of the reaction. Using this approach, a stream of relatively concentrated solids (and cellulase enzymes) can be used to increase the final sugar concentration within the reactor without requiring the high initial levels of insoluble solids that would be required if the operation were performed in batch mode. Experimental application in bench-scale STRs using a feed stream of dilute acid-pretreated corn stover solids and cellulase enzymes resulted in similar cellulose conversion profiles to those achieved in batch shake-flask reactors where temperature control issues are mitigated. Final cellulose conversions reached approximately 80% of theoretical for fed-batch STRs fed to reach a cumulative solids level of 25% (w/w) initial insoluble solids.

Model-Based Fed-Batch for High-Solids Enzymatic Cellulose Hydrolysis

Dynamic optimization of bioprocesses: efficient and robust numerical strategies.

Mycoparasitism-related genes expression of Trichoderma harzianum isolates to evaluate their efficacy as biological control agent

We sought an optimal pH profile to maximize curdlan production in a batch fermentation of Agrobacterium species. The optimal pH profile was calculated using a gradient iteration algorithm based on the minimum principle of Pontryagin. The model equations describing cell growth and curdlan production were developed as functions of pH, sucrose concentration, and ammonium concentration, since the specific rates of cell growth and curdlan production were highly influenced by those parameters. The pH profile provided the strategy to shift the culture pH from the optimal growth condition (pH 7.0) to the optimal production one (pH 5.5) at the time of ammonium exhaustion. By applying the optimal pH profile in the batch process, we obtained significant improvement in curdlan production (64 g L−1) compared to that of constant pH operation (36 g L−1).

Optimal pH control of batch processes for production of curdlan by Agrobacterium species

Chitinases help degradation of cell walls containing chitin and thus accelerates protoplast formation. It indirectly helps strain improvement and development of new strains which are economically viable for industrial use. Chitinases consist of endochitinase, exochitinase, β-N-acetylglucosaminidases and chitobiases. The endochitinases can be further characterized for better understanding of mechanism of the enzyme reaction. This review covers the recent advances in isolation and characterization of endochitinases and its components, gene encoding sequences and cloning.

Characterization and applications of chitinases from Trichoderma harzianum – A review

The optimal control algorithm to calculate the optimal feed rate profile of nutrient solution containing two limiting nutrients was proposed. Different from other conventional optimization methods, the proposed algorithm calculated the optimal control profiles for different initial and feed conditions. The singular optimal control algorithm, dynamic programming, and nonsingular transformation algorithm were used for the optimization of simple problems of the 4th order and the performances were compared. With the proposed transformation algorithm, the final MAb concentration increased and the CPU time decreased. For the different initial glucose and glutamine conditions, the optimal control profiles were calculated with the proposed transformation algorithm. As the initial glutamine concentration increased, the final MAb concentration also increased due to the cell viability increase. This was also applied to the different feed compositions. When the glutamine concentration was increased in the feed stream, the final MAb concentration also increased.

Optimization of feed rate profile for the monoclonal antibody production

Aims: To screen and clone a novel enzyme with specific activity for the resolution of (R)-β-acetylmercaptoisobutyrate (RAM) from (R,S)-β-acetylmercaptoisobutyrate [(R,S)-ester].



Methods and Results:  A micro-organism that produces a novel esterase was isolated and identified as the bacterium Burkholderia cepacia by using the analysis of cellular fatty acids, Biolog automated microbial identification/characterization system, and 16S rRNA gene sequence analysis. A novel esterase gene was cloned from the chromosomal DNA of B. cepacia and was designated as cpoA. The cpoA encodes a polypeptide of 273 amino acids which shows a strong sequence homology with many bacterial nonhaeme chloroperoxidases. In addition, a typical serine-hydrolase motif, Gly-X-Ser-X-Gly, and the highly conserved catalytic triad, Ser95, Asp224, and His253, were identified in the deduced amino acid sequence of cpoA by multiple sequence alignment.



Conclusion:  The cpoA cloned from B. cepacia encodes a novel esterase which is highly related to the nonhaeme chloroperoxidases.



Significance and Impact of the Study:  This is the first report that describes the isolation and cloning of a serine esterase gene from B. cepacia, which is useful in the chiral resolution of (R,S)-ester. The cloned gene will allow additional research on the bifunctionality of the enzyme with esterase and chloroperoxidase activity at the structural and functional levels.

https://sfamjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2672.2004.02262.x

Cloning and expression of a novel esterase gene cpoA from Burkholderia cepacia.

The present invention relates to a segregation reducing agent consisting of curdlan and alkaline materials and a hydraulic composition containing the segragation reducing agent, particularly, the present invention relates to the segregation reducing agent prepared by alkalifying a curdlan-producing fermentation broth per se or a curdlan powder with an alkaline material, and also relates to hydraulic compositions, concrete and mortar, comprising the segregation educing agent. This segregation reducing agent can provide a great segregation reduction effect for hydraulic compositions even at its small amount as well as guarantee the strength, filling ability and fluidity.

J H Lee

Papers

Characterization and applications of chitinases from Trichoderma harzianum – A review

Optimization of feed rate profile for the monoclonal antibody production

Cloning and expression of a novel esterase gene cpoA from Burkholderia cepacia.

Segregation reducing agent consisting of curdlan and alkaline solution and hydraulic composition containing the segregation reducing agent

Influence of agitation speed on production of curdlan by