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Applied Biochemistry and Biotechnology: Part A: Enzyme Engineering and Biotechnology (v.111, #2)
Independent exponential feeding of glycerol and methanol for fed-batch culture of recombinant Hansenula polymorpha DL-1 by H. Moon; S. W. Kim; J. Lee; S. K. Rhee; E. S. Choi; H. A. Kang; I. H. Kim; S. I. Hong (pp. 65-79).
As a novel feeding strategy for aptomizing human epidermal growth factor (hEGF) production with a recombinant Hansenula polymorpha DL-1 using the methanol oxidase (MOX) promoter in H. polymorpha DL-1, independent exponential feeding of two substrates was used. A simple kinetic model considering the cell growth on two substrates was established and used to calculate the respective feeding rates of glycerol and methanol. In the fedbatch culture with methanol-only feeding, the optimal set point of specific growth rate on methanol was found to be 0.10 h−1. When the fed-batch cultures were conducted by the independent feeding of glycerol and methanol, the actual specific growth rate on glycerol and methanol was slightly lower than the set point of specific growth rate. By the uncoupled feeding of glycerol and methanol the volumetric productivity of hEGF increased from 6.4 to 8.0 mg/(L·h), compared with methanol-only feeding.
Keywords: Hansenula polymorpha ; human epidermal growth factor fed-batch; culture; exponential feeding; mixed feed
Degradation of ferric EDTA by Burkhol cepacia by Hung-Yuan Fang; Shin-Chin Chen; Szu-Lin Chen (pp. 81-91).
EDTA, the target compound of this study from the effluent of secondary biotreatment units, can be biodegraded by special microorganisms. So far, there are three species of microorganisms—Agrobacterium, Gram-negative BNCI, and DSM9103—that can degrade EDTA and are published in the literature. We have successfully isolated a bacterial strain that can degrade EDTA. It was identified as Burkhol cepacia, an aerobic species, elliptically shaped with a length of 5–15 μm. The growth medium contains 1000 mg/L of ferric-EDTA as carbon source, 750 mg/L of (NH4)2SO4+(NH2)2CO as nitrogen source, and 1000 mg/L of KH2PO4 as phosphorus source, and mineral factors such as Fe and Mg. Incubated at pH, 7.0, 30°C, and 150 rpm on a shaker for 15 d, the average specific growth rate of this microbe is 0.135 d−1, which shows that the respective degradation efficiency of Fe-EDTA and Cu-EDTA is 90 and 75% individually.
Keywords: EDTA; biodegradation; Burkhol cepacia
Conversion of municipal solid wastes to carboxylic acids by thermophilic fermentation by Wen Ning Chan; Mark T. Holtzapple (pp. 93-112).
The purpose of this research is to generate carboxylic acids from the biodegradable fraction of municipal solid wastes (MSW) and municipal sewage sludge (MSS) by using a thermophilic (55°C), anaerobic, high-solid fermentation. With terrestrial inocula, the highest total carboxylic acid concentration achieved was 20.5 g/L, the highest conversion obtained was 69%, and the highest acetic acid selectivity was 86.4%. Marine inocula were also used to compare against terrestrial sources. Continuum particle distribution modeling (CPDM) was used to predict the final acid product concentrations and substrate conversions at a wide range of liquid residence times (LRT) and volatile solid loading rates (VSLR). “Maps” showing the product concentration and conversion for various LRT and VSLR were generated from CPDM. The predictions were compared to the experimental results. On average, the difference between the predicted and experimental values were 13% for acid concentration and 10% for conversion. CPDM “maps” show that marine inocula produce higher concentrations than terrestrial inocula.
Keywords: Acetic acid; anaerobic; MixAlco; modeling; municipal sewage sludge; municipal solid waste; thermophilic
Activity and survival of spray-dried Beijerinckia sp. Microencapsulated in different carbohydrates by Y. Boza; D. Barbin; A. R. P. Scamparini (pp. 113-128).
This study examined the possibility of preserving Beijerinckia cultures by encapsulation using a spray drier, for use in biotechnological processes in the production of biopolymers. An adequate choice of the wall (coating) material is one of the factors that will determine the degree of cell survival and the maintenance of fermentative activity in the encapsulated inoculum. Malt dextrin, dehydrated glucose syrups, modified starch, and acacia (gum arabic) were used as wall materials. The results showed that spray-dried Beijerinckia encapsulated in malt dextrin, stored for 2 mo, and inoculated into sterile must after rehydration presented the greates stability with respect to fermentative activity, although the glucose-encap sulated cells showed the highest percentage of viability during spray drying and during the storage period.
Keywords: Fermentation; spray drying; Beijerinckia ; encap sulation; biopolymer