Effect Of Bamboo Leaf Flavonoid And Phytic Acid On The Control Efficacy Of Pichia Caribbica Against Penicillium Expansum And Patulin Content In Apple Fruits

Postharvest diseases affect fruits during storage, causing significant economic and nutritional losses leading to food security problems. Generally, severe pathogen infections can result in mycotoxin contaminated foods. Penicillium expansum is the main fungus that causes blue mold disease and the main producer of a mycotoxin called patulin (PAT) in fresh apples and their derivative products. The aim of the study was to determine the effect of exogenous bioactive compounds (bamboo leaf flavonoid and phytic acid) on the biocontrol efficacy of antagonistic yeast, P. caribbica against blue mold caused by P. expansum on apples and its associated production of patulin. The ideal concentrations of bamboo leaf flavonoid (BLF) and phytic acid were established through in vivo and in vitro assays.The results showed that BLF at concentration of 0.01% w/v combined with P. caribbica (1×108 cells/ml) gave additive effects as compared to their separate treatments or untreated control. The combined treatment inhibited wound infection and extension of lesion diameter caused by P. expansum (5×104 spores/ml), significantly (P<0.05). The population growth of P. caribbica in apple wounds increased significantly after treatment with BLF. Intact fruits treated with BLF combined with P. caribbica recorded significantly lower decay incidence of 4% than the control, when stored for 35 days (20℃). Similarly, the combined treatment was 14% lower than the control, when stored for 45 days (4℃) followed by 15 days(20℃). The physical and chemical quality parameters (% weight loss, firmness, total soluble solids, browning index, titratable acidity and ascorbic acid) were not impaired in fruits treated P. caribbica combined with bamboo leaf flavonoid.The interactive effects of P. caribbica and bamboo leaf flavonoid (BLF) on P. expansum were examined in wounds of apple. It was evident that addition of bamboo leaf flavonoid (BLF) to P. caribbica improved the activities of peroxidase (POD), polyphenoloxidase (PPO), superoxide dismutase (SOD), and β-1,3-glucanase as antioxidant enzymes, while catalase (CAT) and malondialdehyde (MDA) activities were suppressed compared with each individual treatments and control. The total phenolic compound (TPC) activity was also stimulated by the combined treatment. The observation using light microscopy and scanning electron microscopy (SEM) indicated positive effect of the combined treatment on increased P. caribbica yeast population to inhibit the growth of fungal hyphae in apple wounds.In this experiment, the reduction of patulin content was investigated in vitro and in vivo. The purpose was to evaluate the prospects of adding bamboo leaf flavonoid as natural bioactive compounds, to P. caribbica in order to reduce patulin accumulation caused by P. expansum (5×104 spores/ml). Specific procedure was used for patulin extraction and determination by HPLC-DAD. From the results, the interaction between P. caribbica treatment and bamboo leaf flavonoid was found to be more efficacious. It also indicated that combine treatment resulted in inhibition of wound lesion diameter, increased lignin contents, regulated pH to> 4.0 at final incubation time and reduced patulin concentration in fruits stored for 18 days at 20℃.The combined treatment of P. caribbica and phytic acid at 0.2% v/v concentration, showed significant improvement in the control of P. expansum infections in apples than either yeast or phytic acid alone. Disease incidence and lesion diameter in treated fruits were significantly lower than the control fruits after 10 days of storage (20 C, RH 95%). P. caribbica treated with or without phytic acid significantly reduced the natural decay incidence, weight loss, browning index, while maintained the firmness, total phenolic compound, total soluble solids (TSS) and titratable acidity (TA) of the applesAlso, the effects of phytic acid addition to P. caribbica on P. expansum growth and defense response activities were investigated. The growth of P. expansum was directly inhibited by phytic acid when studies were done in vitro. The disease defense responses were more pronounced in fruit wounds treated with yeast and phytic acid combined than in their individual treatments or the control. The combined treatment increased peroxidase (POD], polyphenoloxidase (PPO), catalase (CAT] and decreased malondialdehyde (MDA) activities. The study concludes that the activation of defense responses in treated fruits may constitute the basis for increased resistance to the possible future pathogen infection. It was also revealed that indicated that P. caribbica treated with phytic acid can inhibit PAT content, significantly, when in vitro and in vivo tests were conducted.The results suggest that P. caribbica in the presence of exogenous bioactive compounds survives and grows better than yeast alone. Furthermore, the effects of exogenous bioactive compounds on yeasts hold future prospects to control the decay and PAT accumulation on apple caused by P. expansum. Future studies should consider testing the combine treatments on semi-pilot scale storage condition; thus testing the persistence/stabilization processes of different strains of yeast to bamboo leaf flavonoid and phytic acid on apple fruits. Lastly, molecular studies should be conducted to understand the mechanisms of action of exogenous compound-antagonistic yeasts-pathogen interactions effects on patulin content of apple fruit.