耐乙酸粘红酵母合成油脂

乙酸是木质纤维素在水解过程中的主要副产物,高浓度的乙酸严重影响产油微生物的生长和油脂合成。本文研究了粘红酵母对乙酸的耐受性及其利用乙酸合成微生物油脂的能力。结果表明,在初始葡萄糖、木糖浓度分别为6 g/L和44 g/L的混合糖培养基中,乙酸浓度低于10 g/L时,不会对菌体生长产生抑制作用,油脂合成还得到了促进。当乙酸添加量为10 g/L时,生物量、油脂产量、油脂含量较对照组分别提高了21.5%、171.2%和121.6%。进一步研究表明,粘红酵母具备利用乙酸合成油脂的能力,当以乙酸为唯一碳源,浓度为25 g/L时,油脂产量达到3.20 g/L,油脂质量得率为13%。微生物油脂成分分析表明,粘红酵母以乙酸为底物制得的油脂可以作为制备生物柴油的油脂原料,其主要成分为棕榈酸、硬脂酸、油酸、亚油酸和亚麻酸,其中饱和脂肪酸和不饱和脂肪酸含量分别为40.9%和59.1%。由于粘红酵母具有利用乙酸合成微生物油脂的能力,在以木质纤维素水解液为原料生产微生物油脂的脱毒过程中,一定浓度的乙酸可以不必脱除。     

Cleavage of Rabbit Myelin Basic Protein by Pepsin

Rapid cleavage of bovine and guinea pig myelin basic proteins by pepsin at pH 6.0 is limited to the Phe-Phe bond in the middle of the molecule. In the rabbit protein, however, rapid cleavages occur elsewhere in addition to the Phe⁸⁷-Phe⁸⁸ bond in regions in which there are amino acid substitutions. Rapid cleavage occurs at the Leu¹⁵¹-Phe¹⁵² bond, at which Ile-151 has been replaced by Leu, the residue that actually contributes the scissile bond. Rapid cleavages occur at the Phe⁴⁴-Phe⁴⁵ and Leu¹⁰⁹-Ser¹¹⁰ bonds, which in the bovine and guinea pig proteins are relatively resistant under the experimental conditions (pH 6.0). The increased susceptibility of these bonds in the rabbit protein appears to be related to the replacement of Gly-46 by Ser and the change in the sequence immediately NH₂-terminal to Leu-109, from Leu-Ser to Thr-Val. These cleavages of the rabbit protein at the four very susceptible bonds have permitted us to isolate peptides (1-44), (45-87), (88-109), (110-151), and (152-168) in high yield. We have also isolated peptides (88-151), (1-14), and (15-44) in low yield; the latter two result from limited cleavage at the relatively resistant Tyr¹⁴Leu¹⁵ bond. Peptide (88-109) has been chromatographically resolved into species differing in the degree of methylation of Arg-105; this resolution is thought to result from differences in hydrogen bonding ability of the guanidinium groups.     

Chemostat cultivation of Candida blankii on sugar cane bagasse hemicellulose hydrolysate

A Candida blankii yeast isolate was grown in sugar cane bagasse hemicellulose hydrolysate at 38 degrees C in carbon-limited chemostat culture. The pretreatment of the acid hydrolysate prior to microbial cultivation consisted of partial neutralization with ammonia and sodium hydroxide, plus the addition of phosphorus, which was the only other growth-limiting nutrient apart from nitrogen. The cell yield coefficient on nitrogen was 16.78. The critical dilution rate was higher (0.35 h(-1)) in diluted hydrolysate than in undiluted hydrolysate (0.21 h(-1)). In undiluted hydrolysate at a dilution rate of 0.1 h(-1) and pH 4, where aseptic procedures proved unnecessary, the cell and protein yield coefficients were 0.53 and 0.26, respectively, and no residual carbon substrates (D-xylose, L-arabinose, D-glucose, and acetic acid) were detected. The cell yield on oxygen increased linearly as a function of dilution rate. The cellular content of protein, carbohydrate, and RNA also increased with an increase in dilution rate, whereas the DNA content decreased slightly. C. blankii has considerable potential for the production of single cell protein from hemicellulose hydrolysate, because of its ability to utilize all of the major carbon substrates in the hydrolysate at a low pH and at a relatively high temperature with a high protein yield. (c) 1992 John Wiley & Sons, Inc.     

A method for chromatographic separation and fluorometric quantification of 2'',3''-cyclic nucleotide-3''-phosphodiesterase reaction products

Treatment of hydrochloric acid with sodium sulfite prior to the acid hydrolysis of bovine pancreatic ribonuclease A has been found to suppress the oxidation of cystine, methionine, and tyrosine without adversely affecting the recoveries of other amino acids. Statistical analysis of the results indicated that the assumption of the independence of the mean and the variance, an assumption commonly used in the evaluation of the effects of various treatments, may not be valid in evaluating antioxidants used in the acid hydrolysis of proteins.     

Effect of controlled substrate feeding on butyric acid production byClostridium tyrobutyricum

Summary Production of butyric acid from wheat flour hydrolysate was studied withClostridium tyrobutyricum. The mode of substrate supply was found a key parameter for fermentation performance as large improvements were obtained by feeding with a non-limiting supply of substrate. With this procedure, increases in product concentration and productivity but also in selectivity and yield for butyrate were obtained. Substrate feeding controlled by the rate of gas production was found preferable to constant rate feeding for reason of convenience and flexibility. In these conditions, a butyrate concentration of 62.8 gl^–1 was obtained with a productivity of 1.25 gl^–1 h^–1, a selectivity of 91.5% and a yield of 0.45 g per g of glucose.     

Isolation of Herbicide-Resistant 4-Hydroxyphenylpyruvate Dioxygenase from Cultured Coptis japonica Cells

4-Hydroxyphenylpyruvate dioxygenase (HPPD) catalyzes the formation of homogentisate from 4-hydroxyphenylpyruvate and O₂. In plants, HPPD has been identified as a molecular target for herbicides. We report the isolation and characterization of a cDNA encoding a HPPD from cultured Coptis japonica cells. Recombinant CjHPPD showed significantly higher half-maximum inhibitory concentration (IC₅₀) values for the HPPD-inhibiting herbicide destosyl pyrazolate than other plant HPPDs.     

Orally administered collagen peptide protects against UVB-induced skin aging through the absorption of dipeptide forms,Gly-Pro and Pro-Hyp

Collagen hydrolysate is a well-known nutritional supplement for the improvement of healthy skin. Here, collagen peptide NS (CPNS) from fish scale was prepared, and its physicochemical properties were investigated. Gly-Pro was revealed as a representative low molecular weight peptide of CPNS, by performing prep-HPLC and LC-MS/MS. CPNS treatment attenuated matrix metalloproteinase-1 production and increased the synthesis of type 1 procollagen in HDF cells. After orally administering CPNS to rats, the plasma concentrations of Gly-Pro and Pro-Hyp increased dramatically. To examine the protective effects of CPNS against ultraviolet B (UVB)-induced photoaging in vivo, the dorsal skins of hairless mice were exposed to UVB and supplemented with CPNS for 12 weeks. The CPNS consumption significantly attenuated UVB-induced wrinkle formation, transepidermal water loss, and epidermis thickness, and increased skin hydration. Collectively, these results suggest that bioactive peptides of CPNS, Gly-Pro and Pro-Hyp, exert beneficial effects on skin health.     

Microbial oil production from rice straw hydrolysate by Trichosporon fermentans

Microbial oil production from sulphuric acid treated rice straw hydrolysate (SARSH) by Trichosporon fermentans was performed for the first time. Fermentation of SARSH without detoxification gave a poor lipid yield of 1.7 g/l, which was much lower than the result with glucose or xylose as the single carbon source (13.6 g/l or 9.9 g/l). The detoxification pretreatment, including overliming, concentration, and adsorption by Amberlite XAD-4 improved the fermentability of SARSH significantly by removing the inhibitors in SARSH. A total biomass of 28.6 g/l with a lipid content of 40.1% (corresponding to a lipid yield of 11.5 g/l) could be achieved after cultivation of T. fermentans on the detoxified SARSH for 8 days. Moreover, besides SARSH, T. fermentans could also utilize mannose, galactose, or cellobiose, in hydrolysates of other natural lignocellulosic materials as the single carbon source to grow and accumulate lipid with a high yield (at least 10.4 g/l). Hence, it is a promising strain for microbial oil production and thus biodiesel preparation from agro-industrial residues, especially lignocellulosic materials.     

Expression of sarco/endoplasmic reticulum Ca ATPase (SERCA) 3 proteins in two major conformational states in native human cell membranes

The SERCA family includes 3 genes (SERCA1-3), each of which giving rise to various isoforms. To date, detailed structural data is only available for the SERCA1a isoform. Here, limited trypsinolysis of either human platelet membranes or recombinant SERCA3a in HEK-293 cells followed by Western blotting using antibodies covering different regions of the SERCA3(a) protein revealed two, kinetically distinct, Early (ETF) and Late (LTF) Tryptic Fragmentations. The ETF uses many tryptic sites while the LTF uses a unique tryptic site. Using site-directed mutagenesis: i) Arg³³⁴, Arg³⁹⁶ and Arg⁶³⁸ were directly assigned to the ETF and ii) Arg¹⁹⁸ was assigned as the only tryptic site to the LTF. Arg⁶⁷¹, Lys⁷¹²/Lys⁷¹³ and Lys⁷²⁸ were also found to modulate the ETF. SERCA inhibitors Tg and tBHQ induced modest inhibition of the ETF. In contrast, the addition of CaCl₂, EGTA or AlF₄⁻ strikingly modified the ETF without any effect on the LTF. Trypsinolysis of the other recombinant SERCA3b-3f isoforms revealed: i) same ETF and LTF as SERCA3a, with variations of the length of the C-terminal fragments; ii) Arg¹⁰⁰² as an additional tryptic site in SERCA3b-3e isoforms. Taken together, the two distinct SERCA3 fragmentation profiles sign the co-expression of SERCA3 proteins in two conformational states in cell membranes.     

Peptic and tryptic digestion of peptides and proteins monitored by capillary electrophoresis with contactless conductivity detection

The feasibility of monitoring the peptic and tryptic digestion of peptides and proteins with capillary electrophoresis using contactless conductivity detection was investigated. The peptide minigastrin I and the proteins cytochrome c from bovine heart, human serum albumin (HSA), myoglobin, and bovine serum albumin (BSA) were digested off-line with pepsin, and the resulting peptide and amino acid fragments were successfully separated and detected by conductivity measurement. Cytochrome c and myoglobin were also subjected to off-line cleavage with trypsin. On-line digestion using the electrophoretically mediated microanalysis (EMMA) approach was demonstrated with cytochrome c and apomyoglobin using trypsin.