The increase in consumer demand for more sustainable packaging materials represents an opportunity for biopolymers utilization as an alternative to reduce the environmental impact of plastics. Cellulose (C) and chitosan (CH) are attractive biopolymers for film production due to their high abundance, biodegradability and low toxicity. The objective of this work was to incorporate cellulose nanocrystals (NC) and C extracted from corn cobs in films added with chitosan and to evaluate their properties and biodegradability. The physicochemical (water vapor barrier, moisture content, water solubility and color) and mechanical properties of the films were evaluated. Component interactions using Fourier-transform infrared (FTIR) spectroscopy, surface topography by means of atomic force microscopy (AFM), biodegradability utilizing a fungal mixture and compostability by burying film discs in compost were also determined. The C-NC-CH compared to C-CH films presented a lower moisture content (17.19 ± 1.11% and 20.07 ± 1.01%; w/w, respectively) and water vapor permeability (g m⁻¹ s⁻¹ Pa⁻¹ × 10⁻¹²: 1.05 ± 0.15 and 1.57 ± 0.10; w/w, respectively) associated with the NC addition. Significantly high roughness (Rq = 4.90 ± 0.98 nm) was observed in films added to NC, suggesting a decreased homogeneity. The biodegradability test showed larger fungal growth on C-CH films than on CH films (>60% and <10%, respectively) due to the antifungal properties of CH. C extracted from corn cobs resulted in a good option as an alternative packaging material, while the use of NC improved the luminosity and water barrier properties of C-CH films, promoting strong interactions due to hydrogen bonds.

Scheffersomyces stipitis shows a high capacity to ferment xylose, with a strong oxygen dependence to allow NAD⁺ regeneration. However, without oxygen regeneration of NADH occurs by other metabolic pathways like alcoholic fermentation. There are few reports about inhibitors of mitochondrial respiration and their effects on growth and fermentation. This work aimed to explore the effect of cytochrome bc₁ complex inhibition by antimycin A (AA), on growth and fermentation of S. stipitis using glucose, xylose, and arabinose as carbon sources, at three agitation levels (0, 125 and 250 rpm). It was possible to discriminate between respiratory and fermentative metabolism in these different conditions using xylose or arabinose. Despite the inhibition of mitochondrial respiration, the glycolytic flux was active because S. stipitis metabolized glucose or xylose to produce ATP; on 0.5 M glucose the cells yielded 17–33 g L⁻¹ ethanol. However, more complex results were obtained on xylose, which depended upon agitation conditions where ethanol production without agitation increased up to 11 g L⁻¹. Inhibition of respiratory chain in S. stipitis could therefore be a good strategy to improve ethanol yields

Smart packaging is an alternative that may not only replace plastic containers, but also enable food quality monitoring. In this study, an innovative packaging system was developed using a starch-chitosan polymer matrix, infused with rosemary essential oil (REO) as an antimicrobial agent, and betalain extract as a food quality indicator. Betalain extract, derived from beet waste, can change color with pH, making it a useful natural indicator for monitoring food freshness. This packaging system is beneficial for foods that produce metabolites related to degradation, which alter pH and allow for the visual detection of changes in product quality. The objective of this work was to develop a smart packaging system with betalains and rosemary essential oil (REO) to extend food shelf life and monitor quality during storage. REO demonstrated antimicrobial activity, but its effect did not differ significantly among the microorganisms tested. On the other hand, the betalain extract (35.75% BE v/v) completely inhibited the growth of Listeria innocua and Salmonella spp. at concentrations of 50% (v/v; 0.82 ± 0.04 mg betalain/g), showing its potential as an antimicrobial agent. The interactions between chitosan and betalains were primarily associated with electrostatic interactions between the positively charged amino groups of chitosan and the negatively charged carboxyl groups of betalains. In contrast to starch, these interactions could result from interactions between the C=O groups of betalain carboxyls and water, which, in turn, interact with the hydroxyl groups of starch through hydrogen bonding. Despite the results obtained in this study, certain limitations need to be addressed in future research, such as the variability in antimicrobial activity among different bacterial strains, which could reveal differences in the efficacy of betalains and essential oils against other pathogens.