Sugarecane molasse and vinasse added as microbial growth substrates increase calcium carbonate content, surface stability and resistance against wind erosion of desert soils.

Wind erosion is one of the main factors of soil degradation and air pollution in arid and semi-arid regions. In this study we evaluated microbial-induced carbonate precipitation (MICP) as an alternative soil conservation method against wind erosion using sugar cane molasse and vinasse as growth substrates in comparison to tryptic soy broth (TSB). The three substrates were applied in laboratory tests with and without addition of MICP cementing solution (1 M urea plus calcium chloride) to two sandy soils differing in calcium carbonate content. The performance of MICP solution inoculated with a cultured urease-producing strain of Sporosarcina pasteurii was compared to that of an autoclaved MICP solution. For control we also performed a blank treatment without substrate, MICP solution and inoculation. In addition to lab tests in which we determined the effects of treatments on soil pH, electrical conductivity (EC), calcium carbonate (CaCO3) content and surface penetration resistance, we performed wind tunnel experiments to determine soil loss by deflation under different wind velocities. Applying vinasse and molasse strongly increased soil CaCO3 content and penetration resistance, with and without addition of inoculated or non-inoculated MICP solution. Vinasse generally had stronger effects than molasse, while TSB was less effective, especially on penetration resistance. The addition of MICP solution in most treatments did not enhance but rather decrease the substrate effects. In the treatments with vinasse and molasse, increase in penetration resistance translated into substantially decreased soil loss in the wind tunnel tests, down to around one third of the loss in the blank treatment. In contrast, soil loss substantially increased in the treatments with TSB, probably due to the high input of sodium with this substrate. Our results show that molasse and, even more, vinasse can have a strong soil stabilization effect against wind erosion, which is primarily related to the formation of CaCO3 content and does not depend on additional amendments. Thus, these substrates have a great potential to be used on their own as environmentally friendly and cost-effective amendments to control wind erosion of bare sandy soils in arid environments.

Erythritol production with minimum by-product using Candida magnoliae mutant.

In order to enhance erythritol production, mutants of Candida magnoliae DSM70638 were generated by ultraviolet and chemical mutagenesis. Erythritol productivity of samples was analyzed by TLC and HPLC with the refractive index detector. One of the mutants named mutant 12-2 gave a 2.4-fold increase in erythritol (20.32 g/L) and a 5.5-fold decrease in glycerol production compared to the wild strain. A sequence-based map of erythrose reductase gene in this mutant showed a replacement of the A321 by G321 that did not cause any amino acid exchange in protein structure. Therefore, the reason of higher erythritol production in C. magnoliae mutant 12-2 is probably the increase in expression of the open reading frame gene. This study revealed that a mutation or minor change in the sequence of genes involved in a production pathway can lead to a significant increase in protein translation.

Screening and identification of newly isolated cellulose-degrading bacteria from the gut of xylophagous termite Microcerotermes diversus (Silvestri).

The aim of the present study was to isolate and characterize the cellulose-degrading bacteria from the gut of the local termite, Microcerotermes diversus (Silvestri), inhabiting the Khuzestan province of Iran. The microorganisms capable of growing in the liquid medium containing cellulose as the only source of carbon were isolated and their cellulolytic activity on CMC-containing media was confirmed by the congo red clearing zone assay. The isolates were identified based on biochemical characteristics and the phylogenetic analysis of 16S rRNA gene fragments. The results of the present study show that three cellulose-degrading bacteria isolated from local termite guts belonged to the genera Acinetobacter, Pseudomonas and Staphylococcus and four cellulose-degrading bacteria belonged to Enterobacteriaceae and Bacillaceae families. Several isolates recovered from separate termite Microcerotermes diversus samples closely clustered in phylogenetic trees indicating high similarity and the abundance of particular cellulolytic strains. Bacillus B5B and Acinetobacter L9B hydrolyzed cellulose faster than the other isolates (with CMCase activity of 1.47 U/mL and 1.22 U/mL, respectively). The stability of CMCase produced by Bacillus B5B over a broad range of pH and high temperature indicated that the enzyme may be of great commercial value.