Monascus species can produce yellow, orange, and red pigments, depending on the employed cultivation conditions. They are classified as natural pigments and can be applied for coloration of meat, fishes, cheese, beer, and pates, besides their use in inks for printer and dyes for textile, cosmetic, and pharmaceutical industries. These natural pigments also present antimicrobial activity on pathogenic microorganisms and other beneficial effects to the health as antioxidant and anticholesterol activities. Depending on the substrates, the operational conditions (temperature, pH, dissolved oxygen), and fermentation mode (state solid fermentation or submerged fermentation), the production can be directed for one specific color dye. This review has a main objective to present an approach of Monascus pigments as a reality to obtaining and application of natural pigments by microorganisms, as to highlight properties that makes this pigment as promising for worldwide industrial applications.

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This article gives an overview of high-cell-density cultures for polyhydroxyalkanoate (PHA) production and their modes of operation for increasing productivity. High cell densities are very important in PHA production mainly because this polymer is an intracellular product accumulated in various microorganisms, so a high cellular content is needed for the polymer production. This review describes relevant results from fed-batch, repeated batch, and continuous modes of operation without and with cell recycle for the production of these polymers by microorganisms. Finally, recombinant microorganisms for PHA production, as well future directions for PHA production, are discussed.

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An alternative way for determining the oxygen mass transfer coef®cient, k L a, based upon the traditional dynamic method, is proposed. The oxygen material balance equation in the liquid phase is integrated after insertion of the oxygen probe response time (®rst order type), and k L a values are determined by employing Marquardt's algorithm, considering as a weighting factor the model's sensitivity with respect to k L a. Bench-scale fermentations of Aspergillus awamori, performed under different agitation (300±700 rpm) and aeration conditions (0.2±0.6 vvm), were utilized for calculating k L a values (0.0283±0.0874 s À1 ), employing three methods: two so-called traditional, the gas balancing and the dynamic methods, and the one proposed here. The latter method is shown to be as reliable as the aforementioned methods but is easier to apply when the oxygen level in the reactor is above the critical value. # 2000 Society of Chemical Industry Keywords: oxygen mass transfer coef®cient; oxygen uptake rate; electrode response time; dynamic methodDissolved oxygen concentration at instant t= t s in eqn (16) (mol m À3 ) C* Dissolved oxygen saturation concentration in liquid phase at gas±liquid interface (mol m À3 ) C 0Dissolved oxygen concentration at t= t 0 (mol m À3 ) C crit Critical dissolved oxygen concentration (mol m À3 ) C e Electrode signal (mol m À3 ) C e0Electrode signal at t= t 0 (mol m À3 ) C es Electrode signal on quasi steady state (mol m À3 ) C Ã ei ith experimental value of dependent variable C e (mol m À3 ) C ei ith calculated value of dependent variable C e obtained from eqns (9) and (10) (mol m À3 ) C s Dissolved oxygen concentration for quasi steady state (mol m À3 ) k e Electrode's sensitivity (s À1 ) k L a Oxygen mass transfer coef®cient (s À1 ) n Number of experimental values n in Inlet dry molar¯ow rate (mol s À1 ) n out Outlet dry molar¯ow rate (mol s À1 ) N Stirrer speed (rpm) Q O2 Speci®c respiration rate (mol kg À1 s À1 ) Q O2 X Molar microbial oxygen uptake rate (mol m À3 s À1 ) rpm Revolutions per minute (min À1 ) R 2 Correlation coef®cient SSR Sum of squares of residuals t Time (s) t 0 Initial time for integration of eqn (10) (s) t s Instant in which the aeration is re-started (eqn (16)) (s) vvm Air volume per liquid volume per minute (m 3 m À3 min À1 ) V Broth fermentation volume (m 3 ) Y Oin Oxygen molar fraction in the inlet gas stream Y Oout Oxygen molar fraction in the outlet gas stream t e Electrode response time (s À1 ) f Speci®c air¯ow rate (vvm or m 3 m À3 min À1