Statistical optimization of medium composition for bacterial cellulose production by Gluconacetobacter hansenii UAC09 using coffee cherry husk extract--an agro-industry waste.

During the production of grape wine, the formation of thick leathery pellicle/bacterial cellulose (BC) at the airliquid interface was due to the bacterium, which was isolated and identified as Gluconacetobacter hansenii UAC09. Cultural conditions for bacterial cellulose production from G. hansenii UAC09 were optimized by central composite rotatable experimental design. To economize the BC production, coffee cherry husk (CCH) extract and corn steep liquor (CSL) were used as less expensive sources of carbon and nitrogen, respectively. CCH and CSL are byproducts from the coffee processing and starch processing industry, respectively. The interactions between pH (4.5- 8.5), CSL (2-10%), alcohol (0.5-2%), acetic acid (0.5- 2%), and water dilution rate to CCH ratio (1:1 to 1:5) were studied using response surface methodology. The optimum conditions for maximum BC production were pH (6.64), CSL (10%), alcohol (0.5%), acetic acid (1.13%), and water to CCH ratio (1:1). After 2 weeks of fermentation, the amount of BC produced was 6.24 g/l. This yield was comparable to the predicted value of 6.09 g/l. This is the first report on the optimization of the fermentation medium by RSM using CCH extract as the carbon source for BC production by G. hansenii UAC09.

Granulosain I, a cysteine protease isolated from ripe fruits of Solanum granuloso-leprosum (Solanaceae).

A new cysteine peptidase (Granulosain I) was isolated from ripe fruits of Solanum granuloso-leprosum Dunal (Solanaceae) by means of precipitation with organic solvent and cation exchange chromatography. The enzyme showed a single band by SDS-PAGE, its molecular mass was 24,746 Da (MALDI-TOF/MS) and its isoelectric point was higher than 9.3. It showed maximum activity (more than 90%) in the pH range 7-8.6. Granulosain I was completely inhibited by E-64 and activated by the addition of cysteine or 2-mercaptoethanol, confirming its cysteinic nature. The kinetic studies carried out with PFLNA as substrate, showed an affinity (Km 0.6 mM) slightly lower than those of other known plant cysteine proteases (papain and bromelain). The N-terminal sequence of granulosain I (DRLPASVDWRGKGVLVLVKNQGQC) exhibited a close homology with other cysteine proteases belonging to the C1A family.

Carbon material and bioenergetic balances of xylitol production from corncobs by Debaryomyces hansenii.

The effect of oxygenation on xylitol production by the yeast Debaryomyces hansenii has been investigated in this work using the liquors from corncob hydrolysis as the fermentation medium. The concentrations of consumed substrates (glucose, xylose, arabinose, acetate and oxygen) and formed products (xylitol, arabitol, ethanol, biomass and carbon dioxide) have been used, together with those previously obtained varying the hydrolysis technique, the level of adaptation of the microorganism, the sterilization procedure and the initial substrate and biomass concentrations, in carbon material balances to evaluate the percentages of xylose consumed by the yeast for the reduction to xylitol, alcohol fermentation, respiration and cell growth. The highest xylitol concentration (71 g/L) and volumetric productivity (1.5 g/L.h) were obtained semiaerobically using detoxified hydrolyzate produced by autohydrolysis-posthydrolysis, at starting levels of xylose (S(0)) and biomass (X(0)) of about 100 g/L and 12 g(DM)/L, respectively. No less than 80% xylose was addressed to xylitol production under these conditions. The experimental data collected in this work at variable oxygen levels allowed estimating a P/O ratio of 1.16 mol(ATP)/mol(O). The overall ATP requirements for biomass production and maintenance demonstrated to remarkably increase with X(0) and for S(0) >or= 130 g/L and to reach minimum values (1.9-2.1 mol(ATP)/C-mol(DM)) just under semiaerobic conditions favoring xylitol accumulation.

Microbial degradation of amygdalin of bitter apricot seeds (Prunus armeniaca).

Amygdalin is a cyanogenic glycoside occurring among others in almonds and bitter apricot seeds with interesting levels of dietary protein. Utilization of seeds for human or animal nutrition requires adequate detoxification. In the present paper, selected filamentous fungi (Mucor circinelloides, Penicillium nalgiovense) and yeasts (Hanseniaspora valbyensis, Endomyces fibuliger) were tested for their in-situ ability to decompose amygdalin. The latter (Endomyces fibuliger) was best able to grow on autoclaved bitter apricot seeds and detoxify them from 30 microMol CN/g dry matter to less than 1 microMol CN/g dry matter after 48 h of incubation at 27 degrees C.