Three white-rot fungi displayed a wide diversity in their response to supplemented aromatic compounds. Pyrogallol stimulated Cerrena unicolor laccase and manganese peroxidase (MnP) synthesis in synthetic medium 2.5- and 2-fold, respectively, whereas 2,4,6-trinitrotoluene (TNT) brought about a 2.8-fold increase in laccase yield by Trametes versicolor in submerged fermentation of ethanol production residue. No effect of the tested aromatic compounds on enzyme secretion by Ganoderma lucidum in mannitol-containing medium was detected. Nevertheless, G. lucidum is a potent producer of laccase in submerged fermentation of wheat bran and enzyme synthesis can be further increased by supplementation of medium with an appropriate inducer. The structure and the concentration of aromatic compounds play an important role in the regulation of enzyme synthesis. The supplementation of synthetic medium with 0.03-0.3 mM TNT or hydroquinone increased the differential rate of laccase synthesis by C. unicolor from 1,267 to 3,125-8,630 U mg biomass(-1) day(-1). Moreover, the same aromatic compound may function as either an inducer or a repressor, depending on the fungus and enzyme studied. Thus, hydroquinone increased 3-fold T. versicolor laccase activity decreasing 2- and 8-fold the yields of MnP and endoglucanase, respectively.

The production of lignocellulolytic enzymes by eleven basidiomycetes species isolated from two ecosystems of Georgia was investigated for the first time under submerged (SF) and solid-state fermentation (SSF) of lignocellulosic by-products. Notable intergeneric and intrageneric differences were revealed with regard to the extent of hydrolase and oxidase activity. Several fungi produced laccase along with hydrolases in parallel with growth during the trophophase, showing that the synthesis of this enzyme is not connected with secondary metabolism. The lignocellulosic substrate type had the greatest impact on enzyme secretion. Some of the substrates significantly stimulated lignocellulolytic enzyme synthesis without supplementation of the culture medium with specific inducers. Exceptionally high carboxymethyl cellulase (CMCase, 122 U ml -1 ) and xylanase (195 U ml -1 ) activities were revealed in SF of mandarin peelings by Pseudotremella gibbosa IBB 22 and of residue after ethanol production (REP) by Fomes fomentarius IBB 38, respectively. The SSF of REP by T. pubescens IBB 11 ensured the highest level of laccase activity (24,690 U l -1 ), whereas the SSF of wheat bran and SF of mandarin peels provided the highest manganese peroxidase activity (570-620 U l -1 ) of Trichaptum biforme IBB 117. Moreover, the variation of lignocellulosic growth substrate provides an opportunity to obtain enzyme preparations containing different ratios of individual enzymes.

In this study, the effects of several key factors to increase spore production by Bacillus subtilis subsp. KATMIRA 1933 were evaluated in shake flask experiments. In a synthetic medium, glucose concentration played a crucial role in the expression of bacilli sporulation capacity. In particular, maximum spore yield (2.3 × 10 spores/mL) was achieved at low glucose concentration (2 g/L), and further gradual increase of the carbon source content in the medium caused a decrease in sporulation capacity. Substitution of glucose with several inexpensive lignocellulosic materials was found to be a reasonable way to achieve high cell density and sporulation. Of the materials tested, milled mandarin peels at a concentration of 40 g/L served as the best growth substrate. In these conditions, bacilli secreted sufficient levels of glycosyl hydrolases, providing slow hydrolysis of the mandarin peel's polysaccharides to metabolizable sugars, providing the bacterial culture with an adequate carbon and energy source. Among nitrogen sources tested, peptone was found to favor spore production. Moreover, it was shown that cheese and cottage cheese whey usage, instead of distilled water, significantly increases spore formation. After optimization of the nutrient medium in the shake flask experiments, the technical feasibility of large-scale spore production by B. subtilis KATMIRA 1933 was confirmed in a laboratory fermenter. The spore yield (7 × 10 spores/mL) obtained using a bioreactor was higher than those previously reported.

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Nine species of white-rot basidiomycetes isolated from the forests of Georgia have been screened for the endoglucanase, xylanase, laccase, and manganese peroxidase production in both glycerol-containing synthetic medium and mandarin peels-based medium. Irpex lacteus and Trametes ochracea expressed the highest hydrolases activity in submerged and solid-state fermentation (SSF), respectively, of ethanol production residue (EPR). Lenzites betulina appeared to be very promising producer of laccase in both synthetic (52.5 U ml-1) and complex (76.7 U ml-1) media. The tested white-rot fungi exhibited quite different responses to growth substrates used. Mandarin peelings, ethanol production residue, and wheat bran appeared to be excellent growth substrates for the production of complex preparations of hydrolases and oxidases. The same substrates as well as walnut pericarp enhanced laccase and MnP secretion. In addition, the ratio of individual enzymes in final preparations significantly depended on growth substrate. Thus, the laccase/MnP ratio changed from 3 to 548 with substitution of EPR by walnut pericarp in submerged fermentation by L. betulina. Usually, the submerged fermentation of lignocellulosic materials was preferable for the target enzyme secretion. However, the SSF of wheat bran was essential for the CMCase production by I. lacteus, L. betulina, and S. hirsutum. The SSF of EPR was preferable for the laccase production by G. resinaceum, L. betulina, and T. ochracea while the SSF of wheat bran favored MnP accumulation as compared to submerged cultivation.

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In the present study, the polysaccharide-hydrolyzing secretomes of Irpex lacteus (Fr.) Fr. (1828) BCC104, Pycnoporus coccineus (Fr.) Bondartsev and Singer (1941) BCC310, and Schizophyllum commune Fr. (1815) BCC632 were analyzed in submerged fermentation conditions to elucidate the effect of chemically and structurally different carbon sources on the expression of cellulases and xylanase. Among polymeric substrates, crystalline cellulose appeared to be the best carbon source providing the highest endoglucanase, total cellulase, and xylanase activities. Mandarin pomace as a growth substrate for S. commune allowed to achieve comparatively high volumetric activities of all target enzymes while wheat straw induced a significant secretion of cellulase and xylanase activities of I. lacteus and P. coccineus. An additive effect on the secretion of cellulases and xylanases by the tested fungi was observed when crystalline cellulose was combined with mandarin pomace. In I. lacteus the cellulase and xylanase production is inducible in the presence of cellulose-rich substrates but is suppressed in the presence of an excess of easily metabolizable carbon source. These enzymes are expressed in a coordinated manner under all conditions studied. It was shown that the substitution of glucose in the inoculum medium with Avicel provides accelerated enzyme production by I. lacteus and higher cellulase and xylanase activities of the fungus. These results add new knowledge to the physiology of basidiomycetes to improve cellulase production.