Microbial processes biomass formation

The following chapter will provide basic biogeochemical knowledge of the formation and decomposition of primary plant biomass initiating SOM formation. Better awareness of these phy-tochcmical and microbial processes is the basis for understanding soil organic matter chemistry and consequently stability. Addition-... 

In this process, sugars, obtained from biomass, are fermented at low pH into cis-muconic acid. The process of microbial muconic adic formation was already described by Frost and coworkers, who developed E. coli WNl/pWN2.248 that synthesized 36.8 g/L of c/s,ci>muconic acid in 22% (mol/mol) yield from glucose after 48 h of culturing under fed-batch fermentation conditions [147]. This strain did not possess the aroE encoded shikamate dehydrogenase preventing the cells to convert 3-dehydroshikimic acid into shikimic acid which is available for production of cis,cis-muconic acid. Optimization of microbial cis.m-muconic acid synthesis required expression of three enzymes not typically found in E. coli. A recent patent application by Bui et al. describes a productivity of 59 g/L cis muconic acid from 248 g/L glucose by a modified E. coli. in a 20 L fermenter in 88 h. 

Nitrate and Ammonium. The transformations of nitrogen species may occur under suitable microbial catalysis (5, 36). Nitrate reduction may result in formation of either elemental nitrogen or ammonium. Mass balances over a whole lake have indicated the importance of the denitrification process for the elimination of nitrogen from lakes (37). The conditions for the dis-similative ammonification of nitrate are poorly known (36). Ammonium is also released by the mineralization of biomass. 

In direct microbial conversion of lignocellulosic biomass into ethanol that could simplify the ethanol production process from these materials and reduce ethanol production costs, Clostridium thermocellum, a thermoanaerobe was used for enzyme production, hydrolysis and glucose fermentation (755). Cofermentation with C thermosaccharolyticum simultaneously converted the hemicellulosic sugars to ethanol. However, the formations of by-products such as acetic acid and low ethanol tolerance are some drawbacks of the process. Neurospora crassa produces extracellular cellulase and xylanase and has the ability to ferment cellulose to ethanol 139). 

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