Single-step fermentation

Altaf, M., Naveena, B.J., Venkateshwar, M., Kumar, E.V., and Reddy, G. 2006. Single step fermentation of starch to 1(+) lactic acid by Lactobacillus amylophi-lus GV6 in SSF using inexpensive nitrogen sources to replace peptone and yeast extract—Optimization by RSM. Proceedings in Biochemistry 41 465-472. 

Therefore, if the vitamin C or its direct precursor, 2-KLG, could be produced by one single step fermentation process, the final cost of the vitamin C will be significantly decreased. Current research on the one-step fermentation process is focnsed mainly on the following three aspects (1) Classical two-step based one-step fermentation process for 2-KLG production (2) Innovative two-step based one-step fermentation process 2-KLG (3) Direct production of vitamin C from glucose. 

It was almost immediately recognised that the deacylated product, 7-aminocephalosporanic add (7-ACA, Figure 6.16), would be of similar importance as was 6-APA in the development of new penidllins. However, 7-ACA, the cephalosporin equivalent of 6-APA, could not be found in fermentations of Cephalosporin acremonium. In Figure 6.15 we have shown that penicillin acylase hydrolyses the acyl residue from natural cephalosporins. Up to a point this is true. These acylases will, however, only work with a limited range of acyl residues. It now seems that nature does not provide for acylases or transacylases that have the capacity to remove or change the D-a-aminoadipyl side chain of cephalosporin C efficiently in a single step. Widespread search for such an enzyme still remains unsuccessful. 

Regardless of the location of the protein and its state, cell separation needs to be inemensive, simple, and reliable, as large amounts of fermentation-broth dilute in the desired product may be handled. The objectives are to obtain a well-clarified supernatant and solids of maximum dryness, avoiding contamination by using a contained operation. Centrifugation or crossflow filtration is t ically used for cell separation, and both unit operations can be run in a continuous-flow mode [Datar and Rosen, in Stephanopoulos (ed.), op. cit., pp. 369-503]. In recent years, e3q>anded-bea adsorption has become an alternative. It combines broth clarification and adsorption separation in a single step. 

Diagrams for a synthetic chemical, single reaction step process (Fig. 3) and a typical single product fermentation (Fig. 4) are taken from Wintner s excellent article [ Environmental Controls in the Pharm. Industry. Pharm Eng (April 1993)]. Both flow diagrams feature about the same number of unit operations and start with raw material weighing procedures. The essential difference between the two figures is that the fermentation process features sterilization, inactivation, and preservation unit operations. 

On the contrary, a more efficient splitting of sodium lactate into lactic acid (0.96 kg/kg) and sodium hydroxide (0.93 kg/kg) was obtained using a single step three-compartment bipolar ED process, as that shown in Figure 6A, and no pretreatment of the fermentation broth (Kim and Moon, 2001). 

However, some chemists at Upjohn found a better method. They were able to introduce the troublesome oxygen at carbon 11 by the microbiological fermentation of progesterone to produce 11-hydroxyprogesterone. The microbe, with its highly specific enzymes, was able to accomplish in a single step what required numerous steps for the... 

An example of an expanded bed process for recovery of a Pseudomonas exotoxin from an E. coli system has been recently reported in pilot plant scale.28 A single-step recovery of a secreted recombinant protein has been carried out in expanded-bed mode directly from the fermentation broth without prior cell removal. The fusion protein was designed to have relatively low isoelectric point to enable anionic exchange adsorption at pH 5.5 where most of the E. coli host proteins are not adsorbed. The gene product was secreted to the culture medium of E. coli in high yield and the recovery of the protein was 90% in one step.29... 

The fermentation of carbohydrates and protein are each no doubt mediated by more than one species of bacteria, and so the assumption that this occurs in a single step is a significant simplification. However, the fermentation of hydrogen and the various fatty acids by independent species of methane producing bacteria appears to be quite realistic. 

Volatile Acids Kinetics. In evaluating the methane fermentation kinetics of the three volatile acids chosen for study, it was necessary to consider the process biochemistry and stoichiometry. According to Barker (19), acetic acid is fermented to methane and carbon dioxide in a single step while both propionic and butyric acids are fermented in two steps. In the first step these acids are fermented to acetic acid and methane by species of methanogenic bacteria. The resulting acetic acid is then fermented by different methanogenic species to methane and carbon dioxide. The stoichiometry of these fermentations is shown by the following equations (19). 

In the future, novel developments of liquid membranes for biochemical processes should arise. There are several opportunities in the area of fermentation or cell culture, for the in situ recovery of inhibitory products, for example. Another exciting research direction is the use of liquid membrane for enzyme encapsulation so that enzymatic reaction and separation can be combined in a single step. Chapter 6 by Simmons ial- (49) is devoted to this technique. The elucidation of fundamental mechanisms behind the liquid membrane stability is essential, and models should be developed for the leakage rate in various flow conditions. Such models will be useful to address the effect of parameters such as flow regime, agitation rate, and microdroplet volume... 

In some cases, the substrate must be chemically or biochemically hydrolyzed to low-molecular-weight fermentable compounds prior to fermentation. Two steps are then needed to carry out the overall transformation, namely hydrolysis and fermentation. Sometimes, raw substrate hydrolysis is conveniently performed via an enzymatic route, as in the case of ethanol production from cellulose or starch, This two-step transformation can be coupled into a single step in which raw materials are continuously converted to valuable product. 

Bacterial fermentation is used to produce lactic acid from corn starch or cane sugar which is further processed to produce lactide monomer. Because lactic acid is difficult to polymerize directly to high polymers in a single step on a commercial scale, most companies used a two-step process. Lactic acid is first oligomerized to a linear chain with a MW of less than 3,000 by removing water. 

Limonene as a by-product of orange juice production can be used for polymer production together with CO2 to form a polystyrol-like foam. Menthon can be used as a precursor for branched dicarbonic acids and alpha-pinen (a by-product of the forest industry) as precursor for cymol production or for enzymatic verbenone production. Other important terpenoids are phytosterols. They are used in the production of steroid hormones such as cortison or progesteron by Bayer Sobering Pharma. Probably the most important example where plant secondary metabolism and microbial fermentation are synergistically combined, steroid hormones, are produced from phytosterols. A fermentation process by Bayer Schering Pharma uses a plant metaboUte and converts it by a single-step microbial fermentation into the desired end product. 

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