Effect of particle size, packing density and agitation on penicillin production in solid state fermentation

Newly designed multi-stacked circular tray solid-state bioreactor: analysis of a distributed parameter gas balance during solid-state fermentation with influence of variable initial moisture content arrangements

Background

The growth of Aspergillus awamori and Aspergillus oryzae in a self-designed, multi-stacked circular tray solid-state bioreactor (SSB), operating in solid-state fermentation (SSF) conditions at a laboratory scale, was studied. The bioreactor was divided into six layers by six circular perforated trays. Wheat bran was used as both a carrier of bound mycelia and nutrient medium for the growth of A. awamori and A. oryzae. The new tray SSB is equipped with instrumentation (an oxygen (O2)/carbon dioxide (CO2) gas analyser and a thermocouple) to continuously monitor O2 consumption and CO2 and heat evolved, which can directly be used to monitor the fungal biomass. The integrated Gompertz model was used to describe the accumulated evolution of CO2.

Results

The results from the models strongly suggest that the evolved and accumulated CO2 can be used to excellently describe fungal growth. Another important parameter that can be determined by the gas balance method is the respiratory quotient (RQ). This is the ratio of the CO2 evolution rate (CER) to the O2 uptake rate (OUR). The use of CER and OUR confirmed that correlated measurements of microbial activity are available, and the determination of RQ may propose an explanation for differences from expected levels. The kinetic behaviour of the fungal culture, using raw CO2, which represents an accumulation term, was integrated with respect to time and fitted to a Gompertz model, a log-like equation. The model can be used to generate parameter values that may be used to verify the experimental data, and also to simulate and optimise the process.

Conclusion

Overall, A. awamori and A. oryzae have their own ability to degrade and utilise the complex compositions contained in the solid substrate, and fermentation conditions may lead to possible comparisons. In addition, multi-stacked circular tray SSB systems demonstrated an excellent system for further investigations of mass transfer and possibly for large-scale operation, though considerable optimisation work remains to be done; for example, the height/diameter ratio and total number of trays should be optimised.

Utilization of copra waste for the solid state fermentative production of inulinase in batch and packed bed reactors

In this study, screening and optimization of nutrients for inulinase production using copra waste has been studied. Plackett-Burman Design (PBD) was employed to screen the significant nutrients for inulinase production. Response surface methodology (RSM) was used to evaluate the effects of nutrient components in the medium. The second order regression equation provides the inulinase activity as the function of K2HPO4, ZnSO4 · 7H2O and soya bean cake. The optimum conditions are: K2HPO4--0.0047 g/gds, ZnSO4 · 7H2O - 0.02677 g/gds and soya bean cake--0.06288 g/gds. At these optimized conditions, experiments were performed in packed bed bioreactor to optimize the process variables like air flow rate, packing density, particle size and moisture content. The optimum conditions were: air flow rate--0.76 L/min, packing density--38 g/L, particle size--10/14 mesh and moisture content--60%. At the optimized conditions, a maximum inulinase production of 239 U/gds was achieved.

Penicillin production by wild isolates of Penicillium chrysogenum in Pakistan

The present study was aimed at exploring the native wild isolates of Penicillium chrysogenum series in terms of their penicillin production potential. Apart from the standard medium, the efforts were made to utilize suitable agro-industrial wastes for the maximum yield of penicillin. Two series of P. chrysogenum were isolated from local sources and named as P. chrysogenum series UAF R1 and P. chrysogenum series UAF R2. The native series were found to possess better penicillin production potential than the already reported series of P. chrysogenum. However, P. chrysogenum series UAF R1 was found to be the best candidate for high yield of penicillin starting at 100 hour as compared to P. chrysogenum series UAF R2 which produced the highest yield of penicillin at 150 hours for a shorter period of time. Addition of Corn Steep Liquor (CSL) to the fermentation medium resulted in the production of 1.20g/L penicillin by P. chrysogenum series UAF R1 and P. chrysogenum series UAF R2. The fermentation medium in which Sugar Cane Bagasse (SCB) was replaced with CSL resulted in the highest yield of penicillin (1.92g/L) by both native series of P. chrysogenum. The penicillin production was increased by 62.5% in medium with SCB as compared to that with CSL. The penicillin yield of medium containing lactose and phenyl acetate was higher than that of control medium. Overall results revealed that P. chrysogenum series UAF R1 and P. chrysogenum series UAF R2 may be recommended for better yield of natural penicillin and this efficiency may be further enhanced by utilizing SCB as substrate in the growth medium.

Influence of pH regulation and nutrient content on cephalosporin C production in solid-state fermentation by Acremonium chrysogenum C10

AIMS

To investigate the effect of pH regulation and nutrient concentration on cephalosporin C (CPC) production in solid-state fermentation (SSF), using sugarcane bagasse as inert support, impregnated with liquid medium.

METHODS AND RESULTS

Solid-state fermentation using different initial pH values, buffer and nutrient concentrations were performed. Results revealed pH as a key parameter in CPC SSF, as it hampered the antibiotic production not only above 7.8, but also under 6.4. Using initial pH lower than 6.8 and PB in the solid medium, it was possible to keep pH within the production range, increase the production period (from 1 to 3 days) and hence the CPC yield from 468 to 3200 microg gdm(-1) (g(-1) of dry matter).

CONCLUSION

Parameters that help to keep pH in adequate values for CPC production in SSF, such as initial pH, buffering system and nutrient concentration, can greatly increase the production time and CPC yields in this fermentation technique.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first work on CPC production on impregnated support, and the only one revealing pH as a key parameter; it is also shown that high nutrient concentration can improve CPC yields in SSF as long as pH is kept under control.

Production of inulinase by solid-state fermentation: effect of process parameters on production and preliminary characterization of enzyme preparations

This work was aimed at producing inulinase by solid-state fermentation of sugarcane bagasse, using factorial design to identify the effect of corn steep liquor (CSL) and soybean bran concentration, particle size of bagasse and size of inoculum. Maximum inulinase activity achieved was 250 U per g of dry substrate (gds) at 20% (w/w) of CSL, 5% (w/w) of soybean bran, 1 x 10(10) cells mL(-1) and particle size of bagasse in the range 9/32 mesh. The use of soybean bran decreased the time to reach maximum activity from 96 to 24 h and the maximum productivity achieved was 8.87 U gds(-1) h(-1). The maximum activity was obtained at pH 5.0 and 55.0 degrees C. Within the investigated range, the enzyme extract was more thermostable at 50.0 degrees C, showing a D-value of 123.1 h and deactivation energy of 343.9 kJ gmol(-1). The extract showed highest stability from pH 4.5 to 4.8. Apparent K(m) and V(max) are 7.1 mM and 17.79 M min(-1), respectively.

Overview of solid state bioprocessing

Solid-state fermentation has centuries of history, but it is only in the last two decades that there has been a concerted effort to understand the bioprocessing issues involved and to apply them to a wide range of new products. This article provides an overview of the knowledge of solid-state bioprocessing that has been gained over this time. It shows that, although significant advances have been achieved in understanding of what controls process performance, much research is still required.

Production of secondary metabolites by solid-state fermentation

Microbial secondary metabolites are useful high value products that are normally produced by liquid culture; but could be advantageously produced by solid-state fermentation (SSF). Particularly if SSF could benefit from a deeper understanding of microbial physiology in a solid environment. Recent research indicates that different kind of secondary metabolites can be produced by SSF: antibiotics, phytohormones, food grade pigments, alkaloids, etc. Physiology in SSF shows several similarities with physiology in liquid medium, so similar strategies must be adapted for efficient processes. However, there are certain particularities of idiophase in solid medium which dictate the need for special strains.