PubMed · 6791631
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M R Ladisch, J Hong, M Voloch, G T Tsao. 1981. Cellulase kinetics.. https://doi.org/10.1007/978-1-4684-3980-9_5
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Cellulose is a renewable resource with broad biotechnological potential, and its hydrolysis by cellulases underpins applications such as biofuel production and biowaste valorization. This study combined isolation, screening, molecular identification, enzyme assays, genome sequencing, and bioreactor evaluation to characterize novel cellulase-producing bacteria. Preliminary screening identified and selected bacterial isolates by hydrolysis halo formation, with strains showing halos ≥ 20 mm selected for further quantitative assays. Streptomyces olivaceus C1_7A, Bacillus thuringiensis FBB7BB, and Bacillus licheniformis strains AT081C and AT082C showed the highest endoglucanase activities (from 0.11 to 0.26 U mL-1). Further testing on Arundo donax and Avicel led to the selection of B. thuringiensis FBB7BB and S. olivaceus C1_7A as the most promising strains for biotechnological application. Whole genome sequencing confirmed the presence of genes involved in polysaccharide degradation. Finally, lab-scale fermentation trials using 1-2% CMC showed that B. thuringiensis FBB7BB reached a maximum endo-1,4-β-glucanase activity of 0.30 ± 0.04 U mL-1 after 8 h at 37 °C, whereas S. olivaceus C1_7A achieved 0.36 ± 0.03 U mL-1 after 216 h at 30 °C.
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We examined the effects of inhibition of mitochondrial functions on the expression of two nuclear genes encoding the extracellular cellobiohydrolase I (cbh1) and endoglucanase I (egl1) of the cellulase system of the filamentous fungus Trichoderma reesei. The cbh1 and egl1 transcripts are repressed at a low oxygen tension, and by glucose at a concentration known to repress mitochondrial respiration. The transcripts are also down-regulated by chemical agents known to dissipate the proton electrochemical gradient of the inner mitochondrial membrane and blocking of the electron-transport chain, such as DNP and KCN, respectively. These results suggest that expression of those transcripts is influenced by the physiological state of the mitochondria. In addition, heterologous gene fusion shows that the sensitivity of the expression of those transcripts to the functional state of the mitochondria is transcriptionally controlled through the 5'-flanking DNA sequence of those genes.