Computer control of fermentation processes

A review of computer control of fermentation processes is presented. Hardware and software technologies that have been used to implement computer control are discussed. This includes instrumentation, interfacing techniques, computer hardware configurations, data logging and documentation, displays and man-machine interaction, low-level control, back-up and error detection and programming techniques. Advanced control of fermentation processes with the utilization of modern control techniques is also presented. This topic is divided into steady state optimization and dynamic optimization. Finally, on-line estimation of bioreactor parameters for feedback control is presented.     

Growth yield and energy generation in anaerobically-grown Campylobacter spec.

An anaerobic continuous culture study was made with Campylobacter spec. to determine growth yields under various growth conditions. The growth media contained 0.1% (w/v) yeast extract as carbon source. When grown in an aspartate-limited culture Y _asp ^max was 4.6. Inclusion of formate in the culture medium hardly affected the true growth yield. The number of ATP equivalents generated in the fumaratereductase system was 0.66 and the Y _ATP ^max was 7.0. In the nitrate reduction with formate 1.7 ATP equivalents were generated, and a YNO _3- ^max of 12.2 was observed. The true growth yield obtained with a mixture of lactate and aspartate was lower than that found with aspartate alone.     

Synthesis and degradation of proteins during wheat endosperm development

Synthesis of proteins rich in lysine declines progressively with endosperm development and these proteins appear to be degraded preferentially at later stages. The proteolytic enzymes in extracts of endosperms at a late stage of development release considerably more lysine radioactivity from labelled endosperm proteins as compared with the enzymes in endosperms at an early stage.     

Control of methionine synthesis by lysine in Lemna minor

When Lemna minor was cultured in the presence of 0.25 mM l-lysine, the concentration of free methionine and formyl and methyl tetrahydrofolate (THFA) were decreased. l-lysine, l-homoserine, l-threonine and l-methionine at concentrations up to 8 mM did not affect N¹⁰-formyl THFA synthetase (E.C. 6.3.4.3) and N⁵,N¹⁰-methylene THFA reductase (E.C. 1.1.1.68). In contrast, serine hydroxymethyltransferase (E.C. 2.1.2.1) activity was inhibited by lysine. This inhibition gave a sigmoidal curve when plotted for a range of l-lysine or THFA concentrations. Exogenous lysine also reduced the incorporation of glycine [¹⁴C] and serine [3-¹⁴C] into free and protein methionine. Lysine, which is known to control synthesis of homocysteine in L. minor, may also regulate production of C-1 units for methionine synthesis by inhibition of serine hydroxymethyltransferase.     

Saccharopine and 2-aminoadipic acid in Reseda odorata

2(S),2′(S)-N⁶-(2′-Glutaryl)lysine (l-saccharopine) and 2(S)-2-aminoadipic acid have been isolated from Reseda odorata. When traditional isolation procedures are used l-pyrosaccharopine (5(S),5′(S)-N-(5′-amino-5′-carboxy-pentyl)-2-pyrrolidone-5-carboxylic acid) is formed from l-saccharopine by lactamisation. The degree of lactamisation during various isolation steps has been studied, The amino acids were identified by IR and PMR spectroscopy and the configurations established by enzymic and polarimetric analyses. The contents of saccharopine and 2-amino-adipic acid have been determined relative to the total nitrogen content at various stages in the growth cycle of R. odorata.     

Pyruvate fermentation in Rhodospirillum rubrum and after transfer from aerobic to anaerobic conditions in the dark

The fermentative metabolism of Rhodospirillum rubrum (strain Ha, F₁, S₁) was studied after transfering the cells from aerobic to anaerobic dark culture conditions. Pyruvate was metabolized mainly to acetate and formate, and to a lesser extent to CO₂ and propionate, by all strains. Therefore, pyruvate formate lyase would appear to be the characteristic key enzyme of the dark anaerobic fermentation metabolism in R. rubrum. Strain F₁ and S₁ metabolized the formate further to H₂ and CO₂. It is concluded that this cleavage was catalysed by a formate hydrogen lyase system. Strain Ha was unable to metabolize formate. The cleavage of formate and the synthesis of poly--hydroxy-butyric acid were increased by a low pH value (6.5). Fermentation equations and schemes of the pyruvate metabolism are discussed.     

Preservation of vegetables by microbial activity and radiation

Two locally-produced seasonal vegetables, carrot and patol, were preserved in brine, with and without radiation, with marked changes in their properties as foods and their microbiology. The treated vegetables could be preserved, at optimum salt and irradiation levels, for up to 60 days without becoming unacceptable in terms of appearance, texture, flavour and taste. The optimum salt concentrations for preservation of carrot and patol were 2% (w/v) and 3% (w/v), respectively. The microbial load initially showed an upward trend and then declined after 5 to 10 days of storage. Lactic acid bacteria predominated in treated vegetables.     

Coupling of Fermentation and Esterification: Microbial Esterification of Decanoic Acid with Ethanol Produced via Fermentation

Two different kinds of bioprocess, ethanol fermentation and subsequent microbial esterification, were coupled using Issatchenkia terricola IFO 0933 in an interface bioreactor. The strain produced ethyl decanoate (Et-DA) by esterification of exogenous decanoic acid (DA) with ethanol produced via fermentation. The efficiency of the new coupling system depended on the concentration of glucose in a carrier and DA in an organic phase (decane) in an agar plate interface bioreactor. Optimum glucose content and DA concentration were 4% and 29 mM, respectively.