Pectinases are a big group of enzymes that break down pectic polysaccharides of plant tissues into simpler molecules like galacturonic acids. It has long been used to increase yields and clarity of fruit juices. Since pectic substances are a very complex macromolecule group, various pectinolytic enzymes are required to degrade it completely. These enzymes present differences in their cleavage mode and specificity being basically classified into two main groups that act on pectin “smooth” regions or on pectin “hairy” regions. Pectinases are one of the most widely distributed enzymes in bacteria, fungi and plants. This review describes the pectinolytic enzymes and their substrates, the microbial pectinase production and characterization, and the industrial application of these enzymes.

FMN riboswitches are genetic elements that, in many bacteria, control genes responsible for biosynthesis and/or transport of riboflavin (vitamin B₂). We report that the Escherichia coli ribB FMN riboswitch controls expression of the essential gene ribB coding for the riboflavin biosynthetic enzyme 3,4‐dihydroxy‐2‐butanone‐4‐phosphate synthase (RibB; EC 4.1.99.12). Our data show that the E. coli ribB FMN riboswitch is unusual because it operates at the transcriptional and also at the translational level. Expression of ribB is negatively affected by FMN and by the FMN analog roseoflavin mononucleotide, which is synthesized enzymatically from roseoflavin and ATP. Consequently, in addition to flavoenzymes, the E. coli ribB FMN riboswitch constitutes a target for the antibiotic roseoflavin produced by Streptomyces davawensis.

Streptomyces davawensis is the only organism known to synthesize the antibiotic roseoflavin, a riboflavin (vitamin B ₂ ) analog. Roseoflavin is converted to roseoflavin mononucleotide (RoFMN) and roseoflavin adenine dinucleotide in the cytoplasm of target cells. (Ribo-)Flavin mononucleotide (FMN) riboswitches are genetic elements, which in many bacteria control genes responsible for the biosynthesis and transport of riboflavin. Streptomyces davawensis is roseoflavin resistant, and the closely related bacterium Streptomyces coelicolor is roseoflavin sensitive. The two bacteria served as models to investigate roseoflavin resistance of S. davawensis and to analyze the mode of action of roseoflavin in S. coelicolor . Our experiments demonstrate that the ribB FMN riboswitch of S. davawensis (in contrast to the corresponding riboswitch of S. coelicolor ) is able to discriminate between the two very similar flavins FMN and RoFMN and shows opposite responses to the latter ligands.

Background: The bacterium Bacillus subtilis, which is not a natural riboflavin overproducer, has been converted into an excellent production strain by classical mutagenesis and metabolic engineering. To our knowledge, the enhancement of riboflavin excretion from the cytoplasm of overproducing cells has not yet been considered as a target for (further) strain improvement. Here we evaluate the flavin transporter RibM from Streptomyces davawensis with respect to improvement of a riboflavin production strain. Results: The gene ribM from S. davawensis, coding for a putative facilitator of riboflavin uptake, was codon optimized (ribM _opt ) for expression in B. subtilis. The gene ribM _opt was functionally introduced into B. subtilis using the isopropyl-β-thiogalactopyranoside (IPTG)-inducible expression plasmid pHT01: Northern-blot analysis of total RNA from IPTG treated recombinant B. subtilis cells revealed a ribM _opt specific transcript. Western blot analysis showed that the his₆-tagged heterologous gene product RibM was present in the cytoplasmic membrane. Expression of ribM in Escherichia coli increased [¹⁴C]riboflavin uptake, which was not affected by the protonophore carbonyl cyanide m-chlorophenylhydrazone (CCCP). Expression of ribM _opt supported growth of a B. subtilis ΔribB::Erm^r ΔribU::Kan^r double mutant deficient in riboflavin synthesis (ΔribB) and also deficient with respect to riboflavin uptake (ΔribU). Expression of ribM _opt increased roseoflavin (a toxic riboflavin analog produced by S. davawensis) sensitivity of a B. subtilis ΔribU::Kan^r strain. Riboflavin synthesis by a model riboflavin B. subtilis production strain overproducing RibM was increased significantly depending on the amount of the inducer IPTG. Conclusions: The energy independent flavin facilitator RibM could in principle catalyze riboflavin export and thus may be useful to increase the riboflavin yield in a riboflavin production process using a recombinant RibM overproducing B. subtilis strain (or any other microorganism).