Microbial conversion of waste cooking oil into riboflavin by Ashbya gossypii / Conversão microbiana de óleo de cozinha recolhido em riboflavina por Ashbya gossypii

The conversion of waste cooking oil into riboflavin by Ashbya gossypii was investigated in this paper. The effect of initial pH and the original volume of added waste cooking oil in the medium were evaluated to optimize the fermentation efficiency. The results show that when the initial pH was adjusted to 6.5 and 40 g/L waste cooking oil was added in the medium, no residual waste cooking oil was observed and the riboflavin yield reached 4.78 g/L. During the fermentation process, pH, biomass, free amino nitrogen and reduced sugar were dynamically monitored to evaluate the efficient utilization of waste cooking oil for riboflavin yield. The results show that when pH was kept in the range of 6.5-6.8 during the fermentation process, the levels of free amino nitrogen and reduced sugar could be used more efficiently and the riboflavin yield increased to 6.76 g/L .

A conversão microbiana de óleo de cozinha recolhido em riboflavina por Ashbya gossypii foi investigada nesse estudo. O efeito inicial do pH e o volume original de óleo de cozinha recolhido foram avaliados para otimizar a eficiência de fermentação. Os resultados mostraram que quando o pH inicial foi ajustado para 6.5 e 0g/l de óleo de cozinha adicionado ao meio, nenhum óleo residual foi observado e a riboflavina pura atingiu 4.78g/L. Durante o processo de fermentação, pH, biomassa, amino nitrogênio livre e açúcar reduzido foram monitorados dinamicamente para avaliar a utilização eficiente do óleo de cozinha recolhido por riboflavina. Os resultados mostram que quando o pH é mantido numa amplitude de 6.5-6-8 durante o processo de fermentação, os níveis de amino nitrogênio livres e açúcar reduzido podem ser usados mais eficientemente e a riboflavina pura chega a 6.76 g/L.

Isolation and characterization of an Ashbya gossypii mutant for improved riboflavin production

The use of the filamentous fungus, Ashbya gossypii, to improve riboflavin production at an industrial scale is described in this paper. A riboflavin overproducing strain was isolated by ultraviolet irradiation. Ten minutes after spore suspensions of A. gossypii were irradiated by ultraviolet light, a survival rate of 5.5% spores was observed, with 10% of the surviving spores giving rise to riboflavin-overproducing mutants. At this time point, a stable mutant of the wild strain was isolated. Riboflavin production of the mutant was two fold higher than that of the wild strain in flask culture. When the mutant was growing on the optimized medium, maximum riboflavin production could reach 6.38 g/l. It has even greater promise to increase its riboflavin production through dynamic analysis of its growth phase parameters, and riboflavin production could reach 8.12 g/l with pH was adjusted to the range of 6.0-7.0 using KH2PO4 in the later growth phase. This mutant has the potential to be used for industrial scale riboflavin production.

Construction of Chromosome-Specific BAC Libraries from the Filamentous Ascomycete Ashbya gossypii

It is clear that the construction of large insert DNA libraries is important for map-based gene cloning, the assembly of physical maps, and simple screening for specific genomic sequences. The bacterial artificial chromosome (BAC) system is likely to be an important tool for map-based cloning of genes since BAC libraries can be constructed simply and analyzed more efficiently than yeast artificial chromosome (YAC) libraries. BACs have significantly expanded the size of fragments from eukaryotic genomes that can be cloned in Escherichia coli as plasmid molecules. To facilitate the isolation of molecular-biologically important genes in Ashbya gossypii, we constructed Ashbya chromosome-specific BAC libraries using pBeloBAC11 and pBACwich vectors with an average insert size of 100 kb, which is equivalent to 19.8X genomic coverage. pBACwich was developed to streamline map-based cloning by providing a tool to integrate large DNA fragments into specific sites in chromosomes. These chromosome-specific libraries have provided a useful tool for the further characterization of the Ashbya genome including positional cloning and genome sequencing.