Modeling the influence of water activity and ascospore age on the growth of Neosartorya fischeri in pineapple juice

The ascospores of resistant fungi, Neosartorya fischeri, can survive commercial pasteurization, diminishing the shelf life of these products. The time that the ascospores remain in the environment and the effect that they can cause on mold growth are still unknown. This study is aimed to evaluate the influence of water activity (a(w)) from 0.90 to 0.99 and the ascospore age (I) from 30 to 90 days of vitro incubation on the growth of N. fischeri in pineapple juice by mathematical modeling. The growth parameters on pineapple juice: adaptation phase (lambda), maximum specific growth rate (mu(max)) and maximum diameter reached by the colony (A) were obtained by fitting Modified Gompertz and Logistic models to the experimental data. Both models were able to describe microbial growth in pineapple juice, but the Modified Gompertz model presented a slightly superior performance based on statistical indices (correlation coefficients (R(2)), mean square error (MSE), Bias Factor and Accuracy Factor). The minimum values of lambda and A, calculated by the Modified Gompertz model, were 64.7 h and 6.3 mm, while the maximum values were 178.2 h and 20.8 mm, respectively. The result showed that ascospore age did not influence the growth but a(w) was statistically significant to the growth parameters lambda and A. (C) 2010 Elsevier Ltd. All rights reserved.44123924

Amazon forest response to repeated droughts

The Amazon Basin has experienced more variable climate over the last decade, with a severe and widespread drought in 2005 causing large basin-wide losses of biomass. A drought of similar climatological magnitude occurred again in 2010; however, there has been no basin-wide ground-based evaluation of effects on vegetation. We examine to what extent the 2010 drought affected forest dynamics using ground-based observations of mortality and growth utilizing data from an extensive forest plot network. We find that during the 2010 drought interval, forests did not gain biomass (net change: −0.43 Mg ha-1, CI: −1.11, 0.19, n = 97), regardless of whether forests experienced precipitation deficit anomalies. This loss contrasted with a long-term biomass sink during the baseline pre-2010 drought period (1998 − pre-2010) of 1.33 Mg ha-1 yr-1 (CI: 0.90, 1.74, p < 0.01). The resulting net impact of the 2010 drought (i.e., reversal of the baseline net sink) was −1.95 Mg ha-1 yr-1 (CI:−2.77, −1.18; p < 0.001). This net biomass impact was driven by an increase in biomass mortality (1.45 Mg ha-1 yr-1 CI: 0.66, 2.25, p < 0.001), and a decline in biomass productivity (−0.50 Mg ha-1 yr-1, CI:−0.78, −0.31; p < 0.001). Surprisingly, the magnitude of the losses through tree mortality was unrelated to estimated local precipitation anomalies, and was independent of estimated local pre-2010 drought history. Thus, there was no evidence that pre-2010 droughts compounded the effects of the 2010 drought. We detected a systematic basin-wide impact of drought on tree growth rates across Amazonia, with this suppression of productivity driven by moisture deficits in 2010, an impact which was not apparent during the 2005 event [Phillips et al., 2009]. Based on these ground data, both live biomass in trees and corresponding estimates of live biomass in roots, we estimate that intact forests in Amazonia were carbon neutral in 2010 (−0.07 PgC yr-1 CI:−0.42, 0.23), consistent with results from an independent analysis of airborne estimates of land-atmospheric fluxes during 2010 [Gatti et al., 2014]. Relative to the long-term mean, the 2010 drought resulted in a reduction in biomass carbon uptake of 1.1 PgC, compared to 1.6 PgC for the 2005 event