Gerardo Saucedo-Castañeda

On-line automated monitoring and control systems for CO2 and O2 in aerobic and anaerobic solid-state fermentations

Abstract Two systems for monitoring and control of gases from solid-state cultures have been developed. The first involves on-line automated monitoring of CO 2 and O 2 concentration in exhaust gases from eight fermenters or eight gas sampling ports in a large fermenter. It proved to be efficient in obtaining information on the physiological state and respiration rate of the culture in a real-time process. Furthermore, the specific growth rate (μ) can be estimated reliably by gas measurements in aerobic cultures. The second system is for automated control of exit gases from aerobic solid-state fermentations. It permitted elimination of biomass and temperature gradients in a large fermenter due to the maintenance of culture under non-limiting conditions on oxygen. These two systems have applicability in aerobic and anaerobic solid-state processes and were found to be reliable in a number of fermentation experiments as well as optimization of solid-state fermentation. To our knowledge no earlier report of such versatile and reliable on-line automated monitoring/control systems has appeared.

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

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.

Production of β-N-acetylhexosaminidase of Verticillium lecanii by solid state and submerged fermentations utilizing shrimp waste silage as substrate and inducer

Abstract The aim of this study was to utilise shrimp waste silage both as substrate and inducer of β-N-acetylhexosaminidase of Verticillium lecanii in submerged (SF) and solid state fermentations (SSF), taking advantage of the abundance and composition of crustacean wastes (main commercial source of chitin). β-N-Acetylhexosaminidase was produced in SF (initial pH 6) inoculated with spores or mycelia, 540 and 965.5 U/g of initial dry substrate (U/g IDS), respectively. SSF were carried out using a mixture of shrimp waste silage and sugar cane pith bagasse at initial pH of 6. The increment of moisture content and mycelia as inoculum in SSF improved the enzyme yield significantly and reduced the lag phase, i.e. 75% of moisture content inoculated with spores or mycelia produced 1016 and 1673 U/g IDS, respectively. SSF produced a higher β-N-acetylhexosaminidase yield than SF, but required a longer time (24 h). Specific activity in SSF was only 40% higher than SF, due to impurities from shrimp waste silage and sugar cane bagasse. Shrimp waste silage was an efficient inducer of the extracellular enzyme, compared with media supplemented with sucrose where enzymic activity was not detected.

Production of 6-pentyl-α-pyrone by Trichoderma harzianum in liquid and solid state cultures

Abstract The aim of this work was to compare the production of 6-pentyl-α-pyrone (6-PP), a compound which has a strong coconut-like aroma, by Trichoderma harzianum in liquid and in solid state cultivation (LC and SSC). The same liquid medium was used to impregnate sugarcane pith bagasse, used as support in SSC. The maximum concentration of 6-PP produced by T. harzianum in SSC was 2.8 mg (g dry cell mass) −1 equivalent to 0.9 g l −1 of impregnation medium, which is 17 times higher than that obtained in LC. The glucose consumed to yield 6-PP in SSC was 52 mg (g glucose) −1 , eight times higher than that found in LC.

Criteria for the selection of strains of entomopathogenic fungi Verticillium lecanii for solid state cultivation

The objective of this study was the selection of strains of Verticillium lecanii for solid-state fermentation (SSF) containing cuticle of Sphenarium purpurascens as an inducer of proteases and chitinases. The selection criteria were: growth at low water activity (aW), enzymatic activities (proteases and chitinases) and CO2 production rate. Three strains of V. lecanii were studied ATCC 26854, ATCC 46578 and a wild strain (WS). The strains ATCC 26854 and WS presented the best biomass production at low aW (0.957). Highest rates of clearing zones of casein and chitin were obtained for strains ATCC 26854 and WS. Best results of CO2 production in SSF were obtained by using V. lecanii ATCC 26854 which showed a maximal value (2.3 mg CO2 g IDM−1 h−1) at 36 h of cultivation. Although clearing zones of casein and chitin were partial criteria for strain selection. It was concluded that growth a low water activities and CO2 production rate, were more reliable criteria for selecting strains of V. lecanii for solid state culture using cuticle of insect as the main C and N source.

Effect of substrate composition on the mycelial growth of Pleurotus ostreatus. An analysis by mixture and response surface methodologies

Abstract The effect of the composition of a mixture containing, oat straw (OS), oat bran (OB) and copra cake (CC), on the mycelial growth of Pleurotus ostreatus was studied using mixture and response surface methodologies. The applied constraints to the mixtures were: moisture content higher than 70%, C/N ratio less than 30 and total mixture cost less than 2% of the retail cost of fruiting bodies of P. ostreatus. The maximum observed value of apical growth rate (0.50±0.02 cm day−1) was obtained using 0.633, 0.284 and 0.083 (g g−1 mixture, dry basis) for OS, CC and OB mass fractions, respectively. Under these conditions the C/N ratio was 22.4–23.2. Loss of dry matter decreased from 16.9 to 8.5% as the OS fraction (lignin and cellulose source) was increased from 0.55 to 0.80 (g g−1 mixture, dry basis). The utilisation of mixture and response surface methodologies was an useful approach to evaluate the relationship between substrate composition and mycelial development of P. ostreatus.

Review on technological and scientific aspects of feruloyl esterases: A versatile enzyme for biorefining of biomass

With increasing focus on sustainable energy, bio-refining from lignocellulosic biomass has become a thrust area of research. With most of the works being focused on biofuels, significant efforts are also being directed towards other value added products. Feruloyl esterases (EC. 3.1.1.73) can be used as a tool for bio-refining of lignocellulosic material for the recovery and purification of ferulic acid and related hydroxycinnamic acids ubiquitously found in the plant cell wall. More and more genes coding for feruloyl esterases have been mined out from various sources to allow efficient enzymatic release of ferulic acid and allied hydroxycinnamic acids (HCAs) from plant-based biomass. A sum up on enzymatic extraction of HCAs and its recovery from less explored agro residual by-products is still a missing link and this review brushes up the achieved landmarks so far in this direction and also covers a detailed patent search on this biomass refining enzyme.

Biomass estimation of Aspergillus niger growing on real and model supports in solid state fermentation

Direct hydrolysis of Aspergillus niger mycelium growth on amberlite IRA-900 or sugar cane bagasse on solid state fermentation followed by the analysis of soluble protein by the dye binding method was carried out. Hydrolysis with phosphoric acid 0.25M during 7 min allowed maxima protein extraction available to be measured. Color interference of medium components was not observed, allowing the use of this method for biomass estimation when amberlite IRA-900 or sugar cane bagasse are used as support in solid state fermentation processes.

Protein enrichment of sugar cane by-products using solid-state cultures of Aspergillus terreus

Abstract Solid state cultures of Aspergillus terreus were carried out at different temperatures using sugar cane trash blended with salts and diluted molasses. A phase of respiration related to spore germination was observed. The effect of temperature on mold growth was evaluated in terms of lag phase, μmax and Xmax values. The germination phase was more sensitive to temperature changes than the apical growth phase. Satisfactory protein content (9–10% dry matter) and protein yield (23% of spent sugars) were observed when the temperature was regulated within a medium range (25–35°C). Preliminary data for sealing-up studies regarding temperature distribution and CO 2 evolution are presented.

Effect of moisture content and inoculum on the growth and conidia production by Beauveria bassiana on wheat bran

ABSTRACT The aim of the present work was to study the effect of moisture content and inoculum on the growth and conidia production by Beauveria bassiana on wheat bran (WB).The highest growth rate of B. bassiana 885.2 on WB media was obtained at a w =1.0, with no detected growth at a w < 0.97. Solid-state fermentation (SSF) using WB (66% moisture; a w =1.0) achieved a maximal yield of 1.18x10 10 conidia per gram of dry substrate (gds). This yield decreased one order of magnitude with higher moisture contents or the addition of sugarcane bagasse (SCB) as a texturiser. In SSF using WB (66% humidity),the time to obtain a yield of 1x10 10 conidia/gds, referred to as t 10 , could be predicted using a model considering common inoculum levels and maximal yields. For instance, t 10 was 285 h with an inoculum of 1x10 6 conidia/gds; however, t 10 was reduced to 232 h and 148 for inocula of 7x10 6 and 5x10 7 conidia/gds, respectively. The estimation of t 10 values allowed both comparison between the cultures and prediction of harvesting times in production processes. Values for hydrophobicity were within 90 and 92%, whereas viability averages were around 70% for all the cultures Key words