Optimization of Wickerhamomyces anomalus Fermentation Conditions for Pectinase Production Based on Wet Processing of Arabica Coffee in Yunnan Province

In order to improve the pectin-degrading efficiency in wet processing of Arabica coffee in Yunnan, Box-Behnken design and single factor experiment were used to optimize the fermentation conditions of five pectinolytic Wickerhamomyces anomalus strains from the fermentation broth of Arabica coffee in Baoshan, Yunnan during wet processing with pectase activity as an indicator. The results showed that the five strains all synthesized pectin lyase(PL), polygalacturonase(PG), and pectin methylesterase(PM).Among them, strain CAP5 had strong ability to produce PG and PL,while strain CAP4 secreted a large amount of PM. Under optimized conditions, the activity of PG, PL, and PM of the five strains came in at 250.17~411.20 U/mL, 12.98~16.55 U/mL, and 208.52~322.83 U/mL,respectively. The four factors of nitrogen source concentration,fermentation time, Mn2+ concentration, and pH value were optimized and the optimal pectinase-producing fermentation conditions for five strains were as follows: peptone 2.2 g/L, fermentation time 30 h, Mn2+ 1.5 mmol/L, and pH 4.3. After fermentation under the optimized conditions, the maximum PG activity of CAP5 amounted to 411.20 U/mL, 114.03% higher than that before optimization.Meanwhile, the PG activity of strains CAP3, CAP4, CAP8, and CAP10 increased by 86.74%, 114.55%, 65.79%, and 66.07%,respectively, and the activity of PL and PM of the five strains rose 150.35%~218.56% and 341.07%~418.52%, respectively. These findings suggested that W. anomalus strains could be used as coffee starter and had great potential for the lysis of pectin.

Study of the Action Mode of Wickerhamomyces anomalus against Colletotrichum gloeosporioides

Colletotrichum gloeosporioides is the causal agent of anthracnose disease in fruits and vegetables, representing a global problem. The use of biocontrol agents has proved effective against fungal diseases in a wide variety of products. In this work, the antifungal activity of Wickerhamomyces anomalus against C. gloeosporioides isolated from contaminated avocados was evaluated. The antagonism and volatile compound inhibition were measured on Petri dishes. In the mixed cultures, the mycelia damage was observed by scanning electron microscope （SEM）. Chitinase and glucanase production by the antagonism was quantified by the reducing sugars method, and biofilm formation was evaluated with 1% crystal violet. The yeast W. anomalus could reduce the growth of C. gloeosporioides up to 65% by direct antagonism and 10% by volatile compounds. The antagonist did not allow the conidia germination and mycelia growth in any of the tested formulations. SEM showed mycelial damage caused by W. anomalus. The antagonist showed adhesion to the mycelium by a polysaccharide biofilm. The presence of mycelium stimulated the hydrolytic enzyme production with the maximal activity of 21.4 U/mg for chitinases at 24 h and 10 U/mg for glucanases at 60 h. These results showed that W. anomalus used together different mechanisms to express its antifungal activity against C. gloeosporioides. This study might be the first report for this phytopathogen isolated from avocado fruits, which could represent an opportunity to establish biocontrol of diseases for this agricultural product.

Anomalusins A and B, two new ent-rosane diterpenoids from Mallotus anomalus

Two new ent-rosane type diterpenoids, anomalusins A （1） and B （2）, together with ten known compounds were isolated from the plants of Mallotus anomalus Meer et Chun. The structures of compounds 1 and 2 were fully elucidated on the basis of spectroscopic evidence, and CD analysis.