Antonio M. Martin

Optimization of Phaffia rhodozyma continuous culture through response surface methodology.

Response surface methodology was applied to optimize the growth of the yeast Phaffia rhodozyma in continuous fermentation using peat hydrolysates as substrate. A second-order, complete, factorial design of the experiments was used to develop empirical models providing a quantitative interpretation of the relationships between the two variables studied, dilution rate and pH. Maximum biomass concentration in the fermentor was obtained by employing the following predicted optimum fermentation conditions: a dilution rate of 0.017/h and a pH level of 7.19. A verification experiment, conducted at previously optimized conditions for maximum biomass volumetric productivity (a dilution rate of 0.022/h, and a pH level of 6.90), produced values for biomass concentration, residual substrate concentration, biomass yield, and biomass volumetric productivity that were very close to the predicted values, indicating the reliability of the empirical model. The concentration of the pigment astaxanthin produced by the yeast under the optimized growth conditions was found to be 544 mg astaxanthin/kg dry cell biomass.

Optimization of nitrogen recovery in the enzymatic hydrolysis of dogfish (Squalus acanthias) protein. Composition of the hydrolysates

The recovery of nitrogen in the enzymatic hydrolysis of dogfish shark muscle was optimized by the use of response surface methodology. The optimum values for enzyme/substrate ratio, temperature and pH were found to be 3.7% (w/w), 55.3 degrees C, and 8.3, respectively. The dogfish protein hydrolysate produced under these conditions contained a high crude protein concentration (> 85%), and its high nutritional value was indicated by the presence of all essential amino acids, and by high PER values. These results indicate the potential for dogfish protein hydrolysate to be used in lieu of vegetable proteins as a protein supplement in foods.

Growth parameters for the yeast Rhodotorula rubra grown in peat extracts

Abstract A newly-isolated strain of Rhodotorula rubra, which has been reported to have the ability to synthesize high concentrations of carotenoids, has been adapted and grown in liquid phase using acid extracts of peat as the main substrate source. The growth of the yeast was studied as a function of the medium carbohydrate concentration, pH, time, temperature, and agitation rate. The optimal growth conditions were found to be an initial total carbohydrate concentration of 15 g·l−1, a pH of 5.5, an incubation time of 3.5 d, a temperature of 22°C, and an agitation rate of 200 rpm. Under those conditions, the growth parameters were: approximately 4.8 g· l−1 dry biomass, 70% yield and 32% efficiency. Also, a total β-carotene concentration of 1,256 μg·g−1 dry biomass was produced by the yeast.

An overview of pigment production in biological systems: Functions, biosynthesis, and applications in food industry

Abstract Since times immemorial, colors in the living world have always fascinated and amazed humans and left them wonderstruck; the present study has also been inspired by their provocative and conspicuous nature. The structural colors, wherein a variety of optical properties emerge as a result of the physical nature of the surface of the tissue, are, however, excluded from the present review. To give a brief account, two predominant structural colors encountered in the biological systems are Tyndall blue colors and iridescent colors. The former are produced as a result of light scattering by very small particles, examples being the color of human eyes and feathers of many birds. The iridescent colors result from interference with light by thin films or laminations, and examples of such colors are abundant in the animal kingdom, in birds, insects, and fishes. It should be noted that no pigment per se is extractable in either of the structural colors discussed. For a detailed account, the readers may refe...

Influence of process variables on the hydrolysis of shark muscle protein / Influencia de las variables de proceso en la hidrólisis de proteína del músculo de tiburón

Muscle tissue from the spiny dogfish (Squalus acanthias) was enzymatically hydrolysed using a bacterial endopeptidase. The influence of the process variables (temperature, pH, enzyme/ substrate ratio and reaction time) was investigated with regards to the extent of proteolytic degra dation and the recovery of soluble nitrogen from the substrate. Maximum significant nitrogen recovery (NR) was found to be 76.2%, in a 2 h proteolytic reaction. Optimum conditions were 55 °C, pH 8.0 and an enzyme/substrate ratio of 40 mg enzyme/g minced shark muscle (wet weight basis). Under these conditions, a degree of hydrolysis (DH) of 18.6% was obtained. A linear corre lation (R 2 = 0.99) was found to exist between the two measured parameters, NR and DH.

Comparative effects of peat and sawdust employed as bulking agents in composting

Abstract An experimental composting system was employed to compost fish offal and a mixture of chicken manure and crab processing wastes. Peat, sawdust, and mixtures of peat and sawdust were employed as bulking agents for the composting processes. A mixture of chicken manure and crab waste was composted sooner than fish offal, and relationships were observed between the type of bulk material employed and the composition of the composted material.

Studies on the production of Scytalidium acidophilum biomass

SummaryThe conversion of nutrient-supplemented and non-supplemented acid-extracts from peat to biomass of the acid-resistant fungus Scytalidium acidophilum is described. Yeast extract and several inorganic salts were tested as nutrient supplement to the peat extract in shake-flask experiments and in an agitated and aerated fermentor. The best results were obtained in the fermentor, with 0.3% yeast extract, which produced 6.2 g dry biomass/1 with a yield of 41% and an efficiency of 30%, at 200 rpm and 1.75 vvm in 8 days. Although higher agitation speeds appeared detrimental to the mycelial physiology, it was detected that the dissolved oxygen concentration at 200 rpm could limit the growth of S. acidophilum if higher biomass concentrations are obtained. The potential for utilizing the residual fermentation medium as a plant liquid fertilizer is reported.

Submerged growth of Morchella esculenta in peat hydrolysates

SummarySphagnum peat acid hydrolysates have been successfully tested as a culture medium for the submerged growth of the fungus Morchella esculenta in batch fermentations. When glucose and (NH4)2HPO4 are added to the hydrolysate, the concentration of biomass produced is lower than that obtained from nonsupplemented hydrolysates having an equivalent total carbohydrate (TCH) content. Therefore, it appears that the concentration of some essential nutrients (s), as well as the TCH content, is affected by the conditions of hydrolysis.

Mathematical model for Phaffia rhodozyma growth using peat hydrolysates as substrate

The potential of peat hydrolysates for the production of astaxanthin from Phaffia rhodozyma yeast biomass in continuous fermentation was studied. Chemostat fermentations of the yeast were performed using peat hydrolysates as substrate. Kinetic parameters were calculated for the growth of the yeast and the biomass productivity was determined using mathematical models. A low maximum specific growth rate (μ max = 0.08 h -1 ) and a high Monod constant (K s = 26.2 x 10 3 ) were obtained for this substrate. The low maintenance energy requirement found, 0020 g (gh) -1 , confirms the aerobic metabolism of the yeast with this substrate. Under selected conditions, a biomass productivity of 0.108 g (1h) -1 and an astaxanthin productivity of 0.046 mg (1h) -1 were obtained. The biomass produced had a high protein and astaxanthin content (490 ± 8 g kg -1 and 0.43 ± 0.07 g kg -1 , respectively), indicating that it can be used as a feed additive.

Fermentation Processes for the Production of Lactic Acid

As with many other biotechnological processes, lactic acid fermentation has evolved from an ancient “art,” basically associated with the processing and preservation of foodstuffs, to a presently sophisticated technology.