Enhance 1,3-propanediol production from crude glycerol in batch and fed-batch fermentation with two-phase pH-controlled strategy

The batch fermentation of 1,3-propanediol (1,3-PD) by Klebsiella pneumoniae SU6 at different crude glycerol concentration (40-100 g l-1), pH (6.5-7.5) and temperature (31-40\ubaC) combined with two-phase pH-controlled strategy was investigated. Effect of feeding rate (0.10-0.15 L h-1) was studied in fed-batch fermentation. In batch fermentation, the optimal condition was 60 g l-1 crude glycerol, pH control at 6.5 and cultivation temperature at 37\ubaC. The maximum 1,3-PD of 20 g l-1, the yield of 0.34 g 1,3-PD g-1 glycerol consumed and the productivity of 1.25 g l-1 h-1 were achieved at 16 hrs cultivation. The by-products were acetic acid and succinic acid at 2.7 and 1.1 g l-1, respectively. Two-phase pH-controlled strategy gave better results (24.95 g l-1 1,3-PD and 1.78 g l-1 h-1 productivity) than constant pH-controlled strategy (20 g l-1 and 1.25 g l-1 h-1, respectively) at 16 hrs incubation. In fed-batch fermentation, the maximum 1,3-PD of 45.35 g l-1 was achieved at constant feeding rate of 0.1 L h-1. The yield and productivity were 0.44 g g-1 and 1.94 g l-1 h-1, respectively. The fed-batch fermentation with constant feeding at 0.1 L h-1 with two-phase pH-controlled strategy gave 2.2 folds higher 1,3 PD concentration than the batch fermentation with two-phase pH-controlled strategy. This demonstrated the great impact of combination of pH control and feeding strategies in fed-batch fermentation on enhancing 1,3-propanediol production

Pectin at the oil-water interface: Relationship of molecular composition and structure to functionality

The present review examines how macromolecular structure and functional groups of pectin affect its functionality with particular focus on its interfacial activity. We venture into a description of the particularly complex pectin structure and describe the major building blocks and their properties. In the following section, the role of each structural parameter is discussed with particular attention to protein, degree of acetylation and methylation, molecular weight, and branching. Finally, we discuss how modification of the extraction conditions could be tailored to obtain pectin with the desired emulsification properties. It is proposed that pectin with protein content in the range of 3%, with degree of acetylation greater than 10%, molecular weight between 100 and 200 x103 g mol-1 and enriched in RG-I segments is more likely to perform well as an emulsifier. To tailor such a structure, an aqueous extraction protocol with low pH values (between 2.5-3.5) with a strong monoprotic acid (e.g., HCl) and one-step solvent precipitation should be selected. The proposed set of extraction conditions could be used as a first step towards rational design of pectin with desirable interfacial functionality

Enhance 1,3-propanediol production from crude glycerol in batch and fed-batch fermentation with two-phase pH-controlled strategy

The batch fermentation of 1,3-propanediol (1,3-PD) by Klebsiella pneumoniae SU6 at different crude glycerol concentration (40-100 g l-1), pH (6.5-7.5) and temperature (31-40ºC) combined with two-phase pH-controlled strategy was investigated. Effect of feeding rate (0.10-0.15 L h-1) was studied in fed-batch fermentation. In batch fermentation, the optimal condition was 60 g l-1 crude glycerol, pH control at 6.5 and cultivation temperature at 37ºC. The maximum 1,3-PD of 20 g l-1, the yield of 0.34 g 1,3-PD g-1 glycerol consumed and the productivity of 1.25 g l-1 h-1 were achieved at 16 hrs cultivation. The by-products were acetic acid and succinic acid at 2.7 and 1.1 g l-1, respectively. Two-phase pH-controlled strategy gave better results (24.95 g l-1 1,3-PD and 1.78 g l-1 h-1 productivity) than constant pH-controlled strategy (20 g l-1 and 1.25 g l-1 h-1, respectively) at 16 hrs incubation. In fed-batch fermentation, the maximum 1,3-PD of 45.35 g l-1 was achieved at constant feeding rate of 0.1 L h-1. The yield and productivity were 0.44 g g-1 and 1.94 g l-1 h-1, respectively. The fed-batch fermentation with constant feeding at 0.1 L h-1 with two-phase pH-controlled strategy gave 2.2 folds higher 1,3 PD concentration than the batch fermentation with two-phase pH-controlled strategy. This demonstrated the great impact of combination of pH control and feeding strategies in fed-batch fermentation on enhancing 1,3-propanediol production

Effect of co-substrate on production of poly-β- hydroxybutyrate (PHB) and copolymer PHBV from newly identified mutant Rhodobacter sphaeroides U7 cultivated under aerobic-dark condition

Photosynthetic bacterial mutant strain U7 was identified using both classical and molecular (16S rDNA) techniques to be Rhodobacter sphaeroides. The glutamate-acetate (GA) medium containing sodium acetate and sodium glutamate as carbon and nitrogen sources was used for production of poly-β-hydroxybutyrate (PHB) from R. sphaeroides U7 cultivated under aerobic-dark condition (200 rpm) at 37oC. Effect of auxiliary carbon sources (propionate and valerate) and concentrations (molar ratio of 40/0, 40/20, 40/40 and 40/80) on copolymer production were studied. Both combinations of acetate with valerate and acetate with propionate were found to induce the accumulation of poly-β-hydroxybutyrate-co-β-hydroxyvalerate (PHBV) within the cell. Acetate with propionate in the molar ratio of 40/40 gave the highest poly-β-hydroxyalkanoates (PHA) content (77.68%), followed by acetate with valerate at the same molar ratio (77.42%). Although their polymer contents were similar, the presence of 40 mM valerate gave more than 4 times higher hydroxyvalerate (HV) fraction (84.77%) than in the presence of 40 mM propionate (19.12% HV fraction)

Effect of Physical and Enzymatic Modifications on Composition, Properties and In Vitro Starch Digestibility of Sacred Lotus (<i>Nelumbo nucifera</i>) Seed Flour

In this study, native lotus seed flour (N-LSF) was modified by different methods, namely, partial gelatinization (PG), heat–moisture treatment (HMT), or pullulanase treatment (EP). Their composition, functional properties, starch composition, and estimated glycemic index (eGI) were compared. PG contained similar protein, soluble dietary fiber, and insoluble dietary fiber contents to N-LSF, while those of HMT and EP differed from their native form. PG increased rapid digestible starch (RDS) but decreased resistant starch (RS); while HMT and EP increased amylose and RS contents to 34.57–39.23% and 86.99–92.52% total starch, respectively. Such differences led to the different pasting properties of the modified flours rather than PG, which was comparable to the native flour. HMT had limited pasting properties, while EP gave the highest viscosities upon pasting. The eGI of all samples could be classified as low (<50), except that of PG, which was in the medium range (60). It was plausible that lotus seed flour modified either with HMT or EP could be used as carbohydrate source for diabetes patients or health-conscious people

A review on the degradability of polymeric composites based on natural fibres

The applications of natural fibre/polymer composites in civil engineering are mostly concentrated on non-load bearing indoor components due to its vulnerability to environmental attack. This paper evaluates the characteristics of several natural fibre composites exposed to moisture, thermal, fire, and ultraviolet degradation through an extensive literature review. The effects of chemical additives such as fibre treatments, fire retardants and Ultraviolet (UV) stabilizers are also addressed. Based on the evaluation conducted, optimum fibre content provides strength in a polymer composite but it also becomes an entry point for moisture attack. Several fibre treatments are also being used to improve fibre/matrix interface, thereby increasing moisture durability. However, the treated fibres were found to behave poorly when exposed to weather. The addition of UV stabilizers and fire retardants are suggested to enhance outdoor and fire performance of natural fibre/polymer composite but compromises its strength. Therefore, from the collected data and various experimental results, it was concluded that an optimum blend ratio of chemical additives must be employed to achieve a balance between strength and durability requirements for natural fibre composites