RESUMEN
Based on previous bioinformational analysis results, two Aspergillus niger lipase (ANL) mutants, ANL-Ser84Gly and ANL-Asp99Pro were constructed to screen ANL mutants with oil-water interface independence. ANL-Ser84Gly still displayed a pronounced interfacial activation, while ANL-Asp99Pro displayed no interfacial activation. The specific activity of ANL-Ser84Gly towards p-nitrophenyl palmitate (-myristate, -laurate and -decanoate) decreased by 29.8% (53.1, 60.1 and 77.1, respectively) than that of ANL, while the specific activity of ANL-Asp99Pro towards p-nitrophenyl palmitate increased by 2.2-fold. The mutation in the hinge region at both sides of the lid domain also destabilized various secondary structure factors of ANL-S84G and ANL-D99P, which resulted in a substantial decrease in thermostability. The achievement to construct oil-water interface-independent ANL mutants would help to further understand lipase interfacial activation mechanism.
Asunto(s)
Aspergillus niger , Genética , Secuencia de Bases , Estabilidad de Enzimas , Proteínas Fúngicas , Genética , Metabolismo , Lipasa , Genética , Metabolismo , Datos de Secuencia Molecular , Proteínas Mutantes , Genética , Aceites , Especificidad por Sustrato , AguaRESUMEN
High cell density culture of Lactobacillus plantaru is a significant step of the preparation of lactic acid bacteria starter.Firstly,this experiment is designed to analyze the effects of different dissolved oxygen and pH on the batch fermentation of Lactobacillus plantarum.And then,on the base of the batch fermentation,fed-batch fermentation was studied,companied by chemic neutralization in the experiment to achieve the aim of high cell density cultivation.Finally,in the comparison of two kinds of feeding mode for fed-batch operation in 10L fermentor,it was demonstrated that two kinds of feeding mode made cell concentration increase differently,in which pH feedback feeding can control sucrose concentration within a certain lower range,therefore obtaining the maximum cell concentration.With the pH feedback feeding,the dry cell weight was up to 13.56g/L,which increased 90.05% over that of batch culture.
RESUMEN
Lipase from Burkholderia cepacia complex is one of the most versatile biocatalyst and is used widely in many biotechnological application fields including detergent additives, the resolution of racemic compounds, etc. Based on the known whole genomic information of B. cepacia, both ampicillin and kanamycin were added to the TB-T media, the traditional selective media, to screen B. cepacia complex strains from rhizosphere soil samples. The single colonies on the plates with the modified TB-T media were then qualitatively determined the ability to produced the extracellular lipase in the rhodamine B-olive oil agar plates. Thirty-five strains of lipolytic pseudo-B. cepacia complex were isolated and the positive rate of lipolytic bacteria was 65%. Among them, 15 pseudo-B. cepacia complex strains with the tolerance to benzene, n-hexane and n-heptane at the concentration of 10% (V/V) were selected and identified by the recA gene sequence. All of the 15 lipolytic bacteria belonged to the B. cepacia complex.