Gustavo Viniegra-González

Advantages of fungal enzyme production in solid state over liquid fermentation systems

Abstract The present paper attempts to explain why enzyme production in solid-state fermentation (SSF) is higher than in submerged fermentation (SmF). Recent work done in our laboratory [Biotechnol. Lett. 22 (2000) 1255; J. Ind. Microbiol. Biotechnol. 26 (5) (2001) 271; J. Ind. Microbiol. Biotechnol. 26 (5) (2001) 296] related to the production of invertase, pectinases and tannases, by Aspergillus niger grown by SSF and SmF is reviewed. To do such a comparative study, logistic and Luedeking–Piret equations are used in order to estimate the values of the following coefficients: maximal specific growth rate (μM), maximal biomass level (XM), enzyme/biomass yield (YP/X) and secondary rate of production, or breakdown (k). It is shown that enzyme productivity is proportional to group, μMYP/XXM, corrected by a function of ν=k/YP/XμM. In all three cases of enzyme production studied, productivity using a SSF system was higher than in SmF. Studies with invertase resulted in higher values of μMXM. Studies with pectinases resulted in higher values of YP/XXM. Studies with tannases resulted in higher YP/X and less negative values of k. Finally, a reaction–diffusion model is presented to try to explain such differences based on micrographic measurements of mycelial aggregates for each kind of fermentation system.

Effects of different carbon sources on the synthesis of pectinase by Aspergillus niger in submerged and solid state fermentations

A study was made to compare the production of pectinase by Aspergillus niger CH4 in solid-state (SSF) and submerged (SmF) fermentations. Production of endo- (endo-p) and exo-pectinase (exo-p) by SSF was not reduced when glucose, sucrose or galacturonic acid (up to 10%) were added to a culture medium containing pectin. Moreover, both activities increased when concentrations of the carbon sources were also increased. In SmF, these activities were strongly decreased when glucose or sucrose (3%) was added to culture medium containing pectin. The addition of galacturonic acid affected endo-p activity production to a lesser extend than exo-p. Final endo-p and exo-p activities in SSF were three and 11 times higher, respectively, than those obtained in SmF. The overall productivities of SSF were 18.8 and 4.9 times higher for endo-p and exo-p, respectively, than those in SmF. These results indicate that regulatory phenomena, such as induction-repression or activation-inhibition, related to pectinase synthesis by A. niger CH4 are different in the two types of fermentation.

Production and properties of three pectinolytic activities produced by Aspergillus niger in submerged and solid-state fermentation.

Three extracellular pectinases were produced byAspergillus niger CH4 by submerged and solid-state fermentation, and their physicochemical and kinetic properties were studied. The highest productivities of endo- and exo-pectinase and pectin lyase were obtained with solid-state fermentation. The kinetic and physicochemical properties of these enzymes were influenced by the type of culture method used. All activities were very different in terms of pH and temperature optima, stability at different pH and temperature values and affinity for the substrate (Km values). In solid-state fermentation, all pectinase activities were more stable at extreme pH and temperature values but theKm values of endo-pectinase and pectin lyase were higher with respect to those activities obtained by the submerged-culture technique. The pectin lyase activity obtained by the submerged-culture technique showed substrate inhibition but the enzyme obtained by solid-state fermentation did not. Electrophoresis, using sodium dodecyl sulphate/polyacrylamide gel with enzymatic extracts obtained for both culture methods, showed the same number on protein bands but some differences were found in their electrophoretic position. The results obtained in this work suggest that the culture method (submerged or solid-state) may be responsible for inducing changes in some of the pectinolytic enzymes produced byA. niger.

Production of tannase by Aspergillus niger Aa-20 in submerged and solid-state fermentation: influence of glucose and tannic acid

Tannase production by Aspergillus niger Aa-20 was studied in submerged (SmF) and solid-state (SSF) fermentation systems with different tannic acid and glucose concentrations. Tannase activity and productivity were at least 2.5 times higher in SSF than in SmF. Addition of high tannic acid concentrations increased total tannase activity in SSF, while in SmF it was decreased. In SmF, total tannase activity increased from 0.57 to 1.03 IU/mL, when the initial glucose concentration increased from 6.25 to 25 g/L, but a strong catabolite repression of tannase synthesis was observed in SmF when an initial glucose concentration of 50 g/L was used. In SSF, maximal values of total tannase activity decreased from 7.79 to 2.51 IU when the initial glucose concentration was increased from 6.25 to 200 g/L. Kinetic results on tannase production indicate that low tannase activity titers in SmF could be associated to an enzyme degradation process which is not present in SSF. Tannase titers produced by A. niger Aa-20 are fermentation system-dependent, favoring SSF over SmF. Journal of Industrial Microbiology & Biotechnology (2001) 26, 296–302.

Exopectinases produced by Aspergillus niger in solid-state and submerged fermentation: a comparative study

Exopectinase production by Aspergillus niger was compared in submerged fermentation (SmF) and solid-state fermentation (SSF). SSF was carried out using polyurethane foam (PUF) as the solid support. The purpose was to study the effect of sucrose addition (0 or 40 g/l) and water activity level (Aw=0.99 or 0.96) on the level of enzyme activity induced by 15 g/l of pectin. Mycelial growth, as well as extracellular protease production, was also monitored. Sucrose addition in SmF resulted in catabolite repression of exopectinase activity. However, in SSF, an enhancement of enzyme activity was observed. Protease levels were minimal in SSF experiments with sucrose and maximal in SmF without sucrose. Exopectinase yields (IU/g X) were negligible in SmF with sucrose. The high levels of exopectinase with sucrose and high Aw in SSF can be explained by a much higher level of biomass production without catabolite repression and with lower protease contamination. Journal of Industrial Microbiology & Biotechnology (2001) 26, 271–275.

Induction and repression patterns of fungal tannase in solid-state and submerged cultures

Induction and repression patterns of tannase production by Aspergillus niger Aa-20 in solid-state (SSC) and submerged culture (SmC) were established. Tannic acid and glucose were used as carbon sources. Induction and repression ratios were obtained with different concentrations of tannic acid and glucose, respectively. Tolerance to high concentrations of tannic acid by A. niger Aa-20 was lower in SmC than in SSC. In SSC an increase in tannic acid enhanced the expression of tannase activity. The addition of glucose (>20 g l−1) resulted in strong catabolite repression in SmC system. The tannase/biomass yield in SSC was at least 2 times higher than in SmC. The results presented demonstrate the capacity of SSC to minimize catabolite repression. The role of gallic acid in tannase regulation was also studied.

Pectinase-hyperproducing mutants of Aspergillus niger C28B25 for solid-state fermentation of coffee pulp

The uiin of this siid? iiws to improve nrdd strains for the prodiiction of pecriiiases by solid-strite f~riiientation (SSF) qf coffee pirlp. A screening of 248 strains, isolated i11 Mexico’s c(

Invertase production by Aspergillus niger in submerged and solid-state fermentation

fec>-growitig areasv permitted iis 10 select a wild srrain of Aspergillus niger which in 72 !i attains N peak prodiiction of27.7 U rn1-’(138 U g-’ dry pulp) ofpectinase measirred by viscositnetly. Throiigh the tise of (1 selective ciiltitre inediiim wiih low water activity (a,,. = 0.954) witli 2-deo.~y-glircose (ZDG) it itm possible to isolare pectiiiase-h?iperprodi{ctive mutunt strains forSSF (44.5 U tnl-’, 228 U g-’ di? pirlp). Derepressed mirtant strains tlint hyperproduced pectinase by sirbmerged fernretitation (SmF) itwe cilso obtained usitig a classic selective medium with liigli water activity (pectin -+ 2DG) with a,,. = 0.999. A comparison between both classes of mutants, called A W96 and AW99, respectively, points orrt the need to design special selective nrrdia in order to obtain strains adapted either to SSF or SmF in which the a,,. level wodd be a key selecring factor.

Production of pectinases by Aspergillus niger in solid state fermentation at high initial glucose concentrations

Three Aspergillus nigerstrains were grown in submerged and solid state fermentation systems with sucrose at 100 g l−1. Average measurements of all strains, liquid vs solid were: final biomass (g l−1), 11 ± 0.3 vs 34 ± 5; maximal enzyme titres (U l−1) 1180 ± 138 vs 3663 ± 732; enzyme productivity (U l−1h−1) 20 ± 2 vs 87 ± 33 and enzyme yields (U/gX) 128 ± 24 vs 138 ± 72. Hence, better productivity in solid-state was due to a better mould growth.

Degradation and Product Analysis of Caffeine and Related Dimethylxanthines by Filamentous Fungi

Exopectinase (exo-p) and endopectinase (endo-p) production by Aspergillus niger CH4 in solid state culture was studied at initial glucose concentrations of 100, 250, 350 and 450 g/l. The highest activity of exo-p (35 U/g) was produced at 72 and 120 h in the medium containing 100 and 250 g glucose/l, respectively. The maximum endo-p activity (9 U/g) was produced at 72 h in the medium with 250 g glucose/l. The reduction in pectinase production at 350 and 450 g/l initial glucose concentration was due neither to repression of the synthesis of the enzyme nor to the glucose consumption rate of the strain but due to a drastic drop in pH of the medium.