Addition of metal ions to a (hemi)cellulolytic enzymatic cocktail produced in-house improves its activity, thermostability, and efficiency in the saccharification of pretreated sugarcane bagasse.

High activity and stability are essential for (hemi)cellulolytic enzymes used in biomass conversion, while non-productive binding of cellulases to lignin reduces saccharification efficiency and needs to be avoided. One potential strategy is the addition of inexpensive metal ions. This paper describes the influence of divalent metal ions on the activity, thermostability, and saccharification efficiency of (hemi)cellulolytic enzymes produced in-house by Aspergillus niger under solid-state fermentation (SSF). The use of Mn(2+) provided the best (hemi)cellulolytic activity and stability, with an increase in endoglucanase activity of up to 57%. The use of Mn(2+) was then investigated in the saccharification of sugarcane bagasse submitted to acid, steam-explosion, and hydrothermal pretreatments. The addition of Mn(2+) ions at 10mM in the saccharification of acid-pretreated bagasse resulted in a 34% increase in glucose release. These positive effects appeared to be due to a reduction in non-productive enzyme adsorption. The findings suggest that the addition of inexpensive metal ions can help to improve activity, thermostability, and saccharification efficiency of (hemi)cellulolytic enzymes.

An innovative biocatalyst for production of ethanol from xylose in a continuous bioreactor.

The use of the hemicellulose fraction of biomass may be important for the feasibility of the production of second generation bioethanol. Wild strains of Saccharomyces cerevisiae are widely used in industry for production of 1st generation ethanol, and the robustness of this yeast is an important advantage in large scale applications. Isomerization of xylose to xylulose is an essential step in this process. This reaction is catalyzed by glucose isomerase (GI). A new biocatalyst is presented here for the simultaneous isomerization and fermentation (SIF) of xylose. GI from Streptomyces rubiginosus was immobilized in chitosan, through crosslinking with glutaraldehyde, and the support containing the immobilized GI (IGI-Ch) was co-immobilized with S. cerevisiae, in calcium alginate gel. The immobilization experiments led to high immobilized protein loads (30-68 mg × g(support)(-1)), high yields (circa of 100%) and high recovered enzyme activity (>90%). The IGI-Ch derivative with maximum activity presented 1700 IU × g(catalyst)(-1), almost twice the activity of a commercial immobilized GI, GENSWEET(®) IGI-HF. At typical operational conditions for xylose SIF operation (pH 5, 30-35 °C, presence of nutrients and ethanol concentrations in the medium up to 70 L(-1)), both derivatives, IGI-Ch and GENSWEET(®) IGI-HF retained app. 90% of the initial activity after 120 h, while soluble GI was almost completely inactive at pH 5, 30 °C. The isomerization xylose/xylulose, catalyzed by IGI-Ch, reached the equilibrium in batch experiments after 4h, with 12,000 IU × L(-1) (7 g(der) × L(-1)), at pH 5 and 30 °C, in the presence of fermentation nutrients. After co-immobilization of IGI-Ch with yeast in alginate gel, this biocatalyst succeeded in producing 12 g × L(-1) of ethanol, 9.5 g × L(-1) of xylitol, 2.5 g × L(-1) of glycerol and 1.9 g × L(-1) of acetate after consumption of 50 g × L(-1) of xylose, in 48 h, using 32.5 × 10(3) IU × L(-1) and 20 g(yeast) × L(-1), at 35 °C and initial pH 5.3.

Influence of mass transfer limitations on the enzymatic synthesis of beta-lactam antibiotics catalyzed by penicillin G acylase immobilized on glioxil-agarose.

Mass transfer effects were investigated for the synthesis of ampicillin and amoxicillin, at pH 6.5 and 25 degrees C, catalyzed by penicillin G acylase immobilized on agarose. The influence of external mass transfer was analysed using different stirring rates, ranging form 200 to 800 rpm. Above 400 rpm, the film resistance may be neglected. Intra-particle diffusion limitation was investigated using biocatalysts prepared with different enzyme loads and agarose with different mean pore diameters. When agarose with 6, 8 and 10% of crosslinking were used, for the same enzyme load, substrates and products concentration profiles presented no expressive differences, suggesting pore diameter is not important parameter. An increase on enzyme load showed that when more than 90 IU of enzyme activity were used per mL of support, the system was influenced by intra-particle mass transfer. A reactive-diffusive model was used to estimate effective diffusivities of substrates and products.

Design of new immobilized-stabilized carboxypeptidase a derivative for production of aromatic free hydrolysates of proteins.

This paper presents stable carboxypeptidase A (CPA)-glyoxyl derivatives, to be used in the controlled hydrolysis of proteins. They were produced after immobilizing-stabilizing CPA on cross-linked 6% agarose beads, activated with low and high concentrations of aldehyde groups, and different immobilization times. The CPA-glyoxyl derivatives were compared to other agarose derivatives, prepared using glutaraldehyde as activation reactant. The most stabilized CPA-glyoxyl derivative was produced using 48 h of immobilization time and high activation grade of the support. This derivative was approximately 260-fold more stable than the soluble enzyme and presented approximately 42% of the activity of the soluble enzyme for the hydrolysis of long-chain peptides (e.g., cheese whey proteins previously hydrolyzed with immobilized trypsin and chymotrypsin) and of the small substrate N-benzoylglycyl-l-phenylalanine (hippuryl-l-Phe). These results were much better than those achieved using the conventional support, glutaraldehyde-agarose. Amino acid analysis of the products of the acid hydrolysis of CPA (both soluble and immobilized) showed that approximately four lysine residues were linked on the glyoxyl agarose beads, suggesting the existence of an intense multipoint covalent attachment between the enzyme and the support. The maximum temperature of hydrolysis was increased from 50 degrees C (soluble enzyme) to 70 degrees C (most stable CPA-glyoxyl derivative). The most stable CPA-glyoxyl derivative could be efficiently used in the hydrolysis of long-chain peptides at high temperature (e.g., 60 degrees C), being able to release 2-fold more aromatic amino acids (Tyr, Phe, and Trp) than the soluble enzyme, under the same operational conditions. This new CPA derivative greatly increased the feasibility of using this protease in the production of protein hydrolysates that must be free of aromatic amino acids.

Optimization of medium and cultivation conditions for capsular polysaccharide production by Streptococcus pneumoniae serotype 23F.

The influence of medium composition and culture conditions on Streptococcus pneumoniae serotype 23F cultivation was investigated in order to develop an industrial method for polysaccharide (PS) production. Acid-hydrolyzed casein (AHC) and dialyzed enzymatically hydrolyzed soybean meal (EHS) were investigated as nitrogen sources, and the vitamin solution of Hoeprich's medium and dialyzed yeast extract as vitamin sources. The influence of initial glucose concentration was also evaluated. In flask experiments, the best nitrogen source for PS production was AHC; EHS yielded small amounts of PS without interfering with bacterial growth. Dialyzed yeast extract provided an approximately 2-fold increase in PS production when compared to Hoeprich's vitamin solution. In a 5-l bioreactor, it was observed that the pneumococcus did not grow under aerobic conditions, CO(2) did not increase PS yield, glucose was inhibitory above 30 g l(-1), and the main glucose catabolism product was lactate, which had an inhibitory effect on cell growth. When anaerobic cultivation was performed under N(2) flow using the optimized medium, 240 mg l(-1) of soluble PS was obtained, which represents a 3-fold increase in yield as compared to that described in the published patent [Yavordios and Cousin (1983) European Patent 0 071515 A1]. Application of these results would considerably simplify upstream and downstream processes for PS production.

Optimization of medium and cultivation conditions for capsular polysaccharide production by Streptococcus pneumoniae serotype 23F

The influence of medium composition and culture conditions on Streptococcus pneumoniae serotype 23F cultivation was investigated in order to develop an industrial method for polysaccharide (PS) production. Acid-hydrolyzed casein (AHC) and dialyzed enzymatically hydrolyzed soybean meal (EHS) were investigated as nitrogen sources, and the vitamin solution of Hoeprich's medium and dialyzed yeast extract as vitamin sources. The influence of initial glucose concentration was also evaluated. In flask experiments, the best nitrogen source for PS production was AHC; EHS yielded small amounts of PS without interfering with bacterial growth. Dialyzed yeast extract provided an approximately 2-fold increase in PS production when compared to Hoeprich's vitamin solution. In a 5-l bioreactor, it was observed that the pneumococcus did not grow under aerobic conditions, CO2 did not increase PS yield, glucose was inhibitory above 30 g l-1, and the main glucose catabolism product was lactate, which had an inhibitory effect on cell growth. When anaerobic cultivation was performed under N2 flow using the optimized medium, 240 mg l-1 of soluble PS was obtained, which represents a 3-fold increase in yield as compared to that described in the published patent [Yavordios and Cousin (1983) European Patent 0 071515 A1]. Application of these results would considerably simplify upstream and downstream processes for PS production.