Extraction and application of natural silk protein sericin from Bombyx mori as antimicrobial finish for cotton fabrics

In this study, we developed an effective technology for the extraction of sericin from the cocoons of Bombyx mori silk worms. Sericin was extracted with ice cold ethanol to obtain crude extract. Sericin extract was coated onto cotton fabric by a pad–dry–cure method. FTIR characterization of the sericin-coated cotton fabric showed distinct amide peaks. The test organisms that were used in the study to assess the antimicrobial activity of sericin were Escherichia coli and Staphylococcus aureus according to AATCC standard. The antimicrobial activity of the sericin thus extracted was assessed by both qualitative (agar diffusion and parallel streak method) and quantitative (percentage reduction test) methods. An inhibition zone of 28 mm and 30 mm for E. coli and S. aureus by agar diffusion method and a zone of 40 mm and 42 mm for E. coli and S. aureus by parallel streak method were obtained. Quantitative assessment by percentage reduction test showed a reduction percentage of 89.4% and 81% for S. aureus and E. coli, respectively. Results suggested that sericin might be a valuable ingredient for the development of antimicrobial textiles.     

Comparison of growth‐inhibiting activities of Cordyceps militaris and Paecilomyces japonica cultured on Bombyx mori pupae towards human gastrointestinal bacteria

The growth‐inhibiting activities of materials derived from the fruiting body of Cordyceps militaris cultured on Bombyx mori pupae (CM‐1) and pupae separated from the culture (CM‐2), and the fruiting body of Paecilomyces japonica cultured on B. mori pupae (PJ‐1) and pupae separated from the culture (PJ‐2), fresh B. mori larvae (BML), fresh B. mori female pupae (BMP), and Morus alba leaves (MAL) towards eight lactic acid‐producing bacteria and 11 harmful intestinal bacteria were examined using an impregnated paper disc bioassay. At 10 mg per disc, methanolic extracts from CM‐1 and CM‐2 strongly inhibited growth of Clostridium difficile ATCC 9689, C. paraputrificum ATCC 25780, and C. perfringens ATCC 13124 without adverse effects on the growth of eight lactic acid‐producing bacteria and the other eight harmful bacteria. The methanolic extracts from PJ‐1, PJ‐2, BML, BMP, and MAL did not affect growth of all test bacteria. The growth‐inhibiting principle of CM‐1 and CM‐2 towards test clostridia was characterized as cordycepin by spectroscopic analysis. The contents of cordycepin in dried CM‐1 and CM‐2 were 0.69% and 0.54%, respectively. These results suggest that cordycepin may be produced from the fruiting body of C. militaris cultured on B. mori pupae and then translocated to its host insect and accumulated. Structure‐growth inhibition relationships of cordycepin and its eight derivatives against C. perfringens ATCC 13124 indicate that a deoxy form at either 3′ or 2′ position appears critical for the inhibitory activity. Natural cordycepin and its two analogues, 2′‐deoxyadenosine and tubercidin, merit further study as a potential antibacterial agent against various diseases caused by harmful intestinal bacteria such as clostridia. Copyright © 2006 Society of Chemical Industry     

An extracellular lipase from the dimorphic yeast Arxula adeninivorans: molecular cloning of the ALIP1 gene and characterization of the purified recombinant enzyme

The lipase-encoding Arxula adeninivorans ALIP1 gene was isolated using fragments of lipase isolates obtained by trypsin digestion for the definition of oligonucleotide primers in a PCR screening approach. The gene harbours an ORF of 1347 bp encoding a 420 amino acid protein of some 50 kDa preceded by an N-terminal 28 prepro-secretion sequence. The deduced amino acid sequence was found to be similar to the lipases from Candida albicans and C. parapsilosis (34-38% identity) and more distantly related to other lipases. The sequence contains the consensus pentapeptide motif (-Gly-X-Ser-X-Gly-) that forms a part of the interfacial lipid recognition site in lipases. The expression of the gene is regulated by carbon source. In media supplemented with Tween 20, induction of the ALIP1 gene and accumulation of the encoded lipase in the medium is observed, thus demonstrating gene regulation by lipophilic compounds. The enzyme characteristics are analysed from isolates of native strains as well as from those of recombinant strains expressing the ALIP1 gene under control of the strong A. adeninivorans-derived TEF1 promoter. For both proteins a molecular mass of 100 kDa was determined, indicating a dimeric structure, a pH optimum at pH 7.5 and a temperature optimum at 30 degrees C. The enzyme hydrolyses all ester bonds in all triglyceride substrates tested. Middle-sized chain fatty acids are more efficiently hydrolysed than short- and long-chain fatty acids, with the highest activity on C8/C10 fatty acid esters pNP-caprylate, pNP-caprate and tricaprylin.     

Cloning,Sequencing and Expression of a Full-Length cDNA Copy of the M1 Double-Stranded RNA Virus from the Yeast,Saccharomyces cerevisiae

Strains of the budding yeast, Saccharomyces cerevisiae, may contain one or more cytoplasmic viruses with double-stranded RNA (dsRNA) genomes. The killer phenomenon in yeast, in which one cell secretes a killer toxin that is lethal to another cell, is dependent upon the presence of the L-A and M1 dsRNA viruses. The L-A viral genome encodes proteins for the viral capsid, and for synthesis and encapsidation of single-stranded RNA replication cycle intermediates. The M1 virus depends upon the L-A-encoded proteins for its capsid and for the replication of its killer-toxin-encoding genome. A full-length cDNA clone of an M1 genome has been made from a single dsRNA molecule and shown to encode functional killer and killer-immunity functions. The sequence of the clone indicates minor differences from previously published sequences of parts of the M1 genome and of the complete genome of S14 (an internal deletion derivative of M1) but no unreported amino acid variants and no changes in putative secondary structures of the single-stranded RNA. A 118-nucleotide contiguous segment of the M1 genome has not previously been reported; 92 of those nucleotides comprise a segment of A nucleotides in the AU-rich bubble that follows the toxin-encoding reading frame. The GenBank Accession Number for the sequence is U78817; the locus is SCU78817. © 1997 John Wiley & Sons, Ltd.     

Effect of feeding treatment during the backgrounding phase of beef production from pasture on: II. Longissimus muscle proximate composition, cholesterol and fatty acids

This study evaluated effects of feedlot backgrounding strategies (40, 70 or 100% alfalfa hay diets) or pasture grazing on moisture, protein, total lipids, ash, cholesterol concentration, and lipid profiles of the longissimus dorsi muscle (LM) of pasture finished Angus heifers. Ninety six calves were allocated to the strategies over a 114-day period, followed by pasture grazing over 132 days. At the end of the backgrounding stage, the concentration of omega-3 (n-3) fatty acids was highest in the Pasture group and this difference persisted (P < 0.032) until the end of the 132 day pasture finishing phase. Similarly, the n-6/n-3 ratio was lowest in the Pasture group at the end of backgrounding and after pasture finishing. Backgrounding diets based on 70 and 100% hay or pasture grazing showed greater (P < 0.041) conjugated linoleic acid (CLA) concentration in the lipid fraction than 40% hay. Results suggested that residual effects of backgrounding strategies could be detected in intramuscular fat of pasture finished heifers.