Immobilization of Lactobacillus bulgaricus with gellan gum and its application in continuous fermentation of D-lactic acid from corn straw / 生物工程学报

Biorefinery of chemicals from straw is an effective approach to alleviate the environmental pollution caused by straw burning. In this paper, we prepared gellan gum immobilized Lactobacillus bulgaricus T15 gel beads (LA-GAGR-T15 gel beads), characterized their properties, and established a continuous cell recycle fermentation process for D-lactate (D-LA) production using the LA-GAGR-T15 gel beads. The fracture stress of LA-GAGR-T15 gel beads was (91.68±0.11) kPa, which was 125.12% higher than that of the calcium alginate immobilized T15 gel beads (calcium alginate-T15 gel beads). This indicated that the strength of LA-GAGR-T15 gel beads was stronger, and the strain was less likely to leak out. The average D-LA production was (72.90±2.79) g/L after fermentation for ten recycles (720 h) using LA-GAGR-T15 gel beads as the starting strain and glucose as the substrate, which was 33.85% higher than that of calcium alginate-T15 gel beads and 37.70% higher than that of free T15. Subsequently, glucose was replaced by enzymatically hydrolyzed corn straw and fermented for ten recycles (240 h) using LA-GAGR-T15 gel beads. The yield of D-LA reached (1.74±0.79) g/(L·h), which was much higher than that of using free bacteria. The wear rate of gel beads was less than 5% after ten recycles, which indicated that LA-GAGR is a good carrier for cell immobilization and can be widely used in industrial fermentation. This study provides basic data for the industrial production of D-LA using cell-recycled fermentation, and provides a new way for the biorefinery of D-LA from corn straw.

Substract and temperature effect on xylanase production by aspergillus fumigatus using low cost agricultural wastes / Efeito da temperatura e do substrato na produção de xilanase por aspergillus fumigatus utilizando resíduos agroindustriais de baixo custo

This study reports the optimization of xylanase production under solid state fermentation (SSF) by a thermotolerant Aspergillus fumigatus strain (SCB4) isolated from sugarcane bagasse piles of Brazilian Cerrado. Different combinations of low-cost agricultural byproducts in SSF were evaluated: sugarcane bagasse and wheat bran (1:1), sugarcane bagasse and corn straw (1:1) and only sugarcane bagasse. The enzyme biosynthesis by SSF was carried out at different temperatures (40, 45, 50 and 55 oC). The maximum levels of xylanase activity were obtained after 24 h at 45 °C using a culture medium containing sugarcane bagasse and wheat bran (1:1). Under optimal conditions, the fungal culture produced 574 U g-1 of xylanase (units/g of dry substrate). The crude enzyme showed optimal activity at 60 °C and pH 4.5. It exhibited thermostability up to 55 °C, wide range of pH stability and tolerance to ethanol, xylose and glucose. The physicochemical properties shown by this enzyme are appropriate for its application in hydrolysis of lignocellulosic residues for ethanol production and other bioproducts.

Este estudo descreve a otimização da produção de xilanase por fermentação em estado sólido (FES) por uma linhagem termotolerante de Aspergillus fumigatus isolada de pilhas de bagaço de cana-de-açúcar do Cerrado Brasileiro (linhagem SCB4). Combinações de diferentes subprodutos agrícolas de baixo custo foram avaliadas como substratos na FES: bagaço de cana-de-açúcar e farelo de trigo (1:1), bagaço de cana-de-açúcar e palha de milho (1:1) e somente bagaço de cana-de-açúcar. A produção da enzima por FES foi realizada em diferentes temperaturas (40, 45, 50 e 55 oC). Níveis máximos de xilanase (574 U g-1 de substrato seco) foram obtidos após 24 h a 45 °C, utilizando bagaço de cana-de-açúcar e farelo de trigo (1:1) no meio de cultura. O extrato enzimático bruto apresentou atividades ótimas a 60 °C e pH 4,5. A enzima exibiu estabilidade térmica até 55 °C, ampla faixa de pH de estabilidade e tolerância ao etanol, xilose e glucose. Tais propriedades físico-químicas indicam que o extrato enzimático obtido é apropriado para aplicação na hidrólise de resíduos lignocelulósicos para a produção de etanol e outros bioprodutos.

Identification of Chaetomium sp. CQ31 and Optimization of Xylanase Production in Solid State Fermentation / 微生物学通报

A fungus CQ31 isolated from soil samples was identified as Chaetomium sp.. This strain produced effectively xylanases utilizing several liguocellulosic materials in the solid-state fermentation (SSF), and corn straw was the best carbon source. The results of single-factor-experiment showed that the corn straw as the carbon source, tryptone as the nitrogen source, initial moisture content of 80% and initial pH 9.0 were the optimal conditions for xylanase production. Under the optimized conditions, it produced xylanase which was 4897 U/g dry substrate while mannanase was 803 U/g dry substrate after 7 days of cultivation. Therefore, xylanase and mannanase production by Chaetomium sp. CQ31 in SSF possess potential for commercial applications.

Application Research on the Production of Ergosterol using Corn Straw Hydrolyzates Fermentation by Yeast / 微生物学通报

Biomass is a renewable resource, which can be transformed into useful chemical products. The effects of dilute hydrochloric acid on the hydrolysis of steam explosion pretreatment of corn straw were studied. This article developed the application research of ergosterol using corn straw hydrolysates as fer- mentation substrates. The results showed that when corn straw was hydrolyzed with 1.5% hydrochloric acid, temperature at 90?C, hydrolysis for 3 h and the corresponding solid to liquid ratio at 10%, the reducing sugar content can reached up to 53.3% and cellulose conversion efficiency was 79%. The optimal fermental pa- rameters were as follows: 6.0 oBx of corn straw hydrolysates, corn concentration steep water at 4%, pH 7.5, 10% of inoculation, 28?C cultivated for 32 h. Under these conditions, the yeast biomass up to 8.5 g/L and the ergosterol content up to 2.35%. The infrared spectrometer and the X-ray diffract meter used to characterize of crystallite structure.

Study on the Production of Ergosterol Using Corn Straw Hydrolyzates Fermentation / 中国生物工程杂志

The ergosterols were produced from corn straw hydrolysates fermented by ergosterol yeast,which was obtained from protoplast electrofusion.The effects on the yield of ergosterol were studied in the condition of shaker,such as initial sugar concentration,nitrogen source,pH value and fermentation time.The technical conditions were optimized according to the DPS center-united experimental design principles and the method of response surface analysis with four factors and three levels.The results indicated that the four factors had significant correlation to ergosterol accumulation.The biomass and the ergosterol content could be up to 8.67g/L and 2.37% respectively after cultivated for 32h under optimal technical condition.The structure of ergosterol crystal was characterized by UV,IR and SEM.A new approach of biomass source application was presented.