Ana Iraidy Santa Brígida

Lipase production by the strictly aerobic yeast Yarrowia lipolytica is closely related to the content of dissolved oxygen in the culture medium. Some strategies to improve oxygen transfer to microorganisms have already been used, such as the use of perfluorocarbons (PFCs). The present work investigates the influence of agitation speed and the use of perfluorodecalin (PFC) on the profile of the produced lipases. Lipase production increased 2.5-fold with a higher agitation speed (550 to 650 rpm) without PFCs in the medium. The presence of an oxygen carrier led to a significant 91% increase in lipase production at lower shaking speeds compared to the assay without PFC; however, an increase in lipase production was not detected with PFC at 650 rpm. The protein profiles exhibited typical bands for two lipases produced (near 40 and 60 kDa), and these bands became more intense when PFC was added during production, as a result of the large enhancement in lipolytic activity. Additionally, the protein profiles obtained from extracts at 650 rpm were clearer and more selective regardless of the presence of PFC, suggesting an enhancement in specific activity associated with increased shaking. These findings highlight the significant impact of oxygen availability on lipase production, offering valuable insights for industrial applications.

Lipase from Pseudomonas fluorescens (PFL) and laccase from Trametes versicolor were co-immobilized onto nanocellulose (NC), using a layer-by-layer approach. Initially, PFL was adsorbed onto NC through ionic and hydrophobic interactions. To achieve higher PFL immobilization yield and activity, NC was functionalized with aldehyde groups through periodate oxidation (NCox) or glutaraldehyde activation (NC-GA). FTIR analysis confirmed these chemical modifications. Among the functionalized NCs, NCox showed the best capacity to retain higher amounts of PFL (maximum load: 20 mg/g), and this support was selected to proceed with the co-immobilization experiments. In this process, NCox-250-PFL (NCox activated with 250 µmol/g of aldehyde groups) was covered with polyethyleneimine (PEI), laccase was co-immobilized, and a crosslinking step using glutaraldehyde was used to covalently attach the enzymes to the support, producing the biocatalyst NCox-250-PFL-PEI-Lac-GA. Co-immobilized enzymes presented higher thermal stability (50 °C) than soluble enzymes; co-immobilized laccase retained 61.1% of its activity after 24 h, and PFL retained about 90% after 48 h of deactivation at 50 °C. In operational stability assays, the heterogeneous biocatalysts maintained more than 45% of their activity after five cycles of pNPB hydrolysis and ABTS oxidation. This co-immobilized biocatalyst, with its high stability and activity retention, is a promising multi-active heterogeneous biocatalyst for use in cascade reactions of industrial interest.

Micropropagated banana plantlets need acclimatization to reduce the stresses caused by the change from in vitro to ex vitro environment. The objective of this study was to evaluate the influence of thermal stress on the acclimatization of micropropagated plantlets of banana cultivar ‘Prata Catarina’, supplemented with plant growth-promoting rhizobacteria. Four applications of the LPPC159 strain, belonging to the genus Bacillus were performed every 15 days. Inoculated plantlets did not show differences in the biometric variables compared to fertilized plantlets. Plantlets acclimatized for seven days under controlled conditions, seven days in tunnel and 46 days in greenhouse showed greater pseudostem diameter, fresh and dry mass, and higher accumulations of N, P, K, Ca, Mg, S, Na, B, and Cu. No significant differences were observed between inoculated and non-inoculated plantlets. Inoculations had positive and negative effects only on the accumulations of N and Cu, respectively. The lowest thermal indices were observed for plantlets of T5 (7 days in a controlled environment + 7 days in a tunnel + 46 days in a greenhouse) and T1 (14 days in a shade tunnel + 46 days in a greenhouse), promoting better thermal comfort for plantlets of these treatments. Using shade in the acclimatization phase combined with plant growth-promoting rhizobacteria promoted gains in pseudostem diameter, fresh mass, dry mass, and nutrient accumulation in the plantlets. These conditions also allowed reductions in thermal stress in the acclimatization phase of micropropagated plantlets of banana cultivar ‘Prata Catarina’.

A comparative study was perfomed with conventional and ultrasound assisted extraction on tomato processing waste. Ultrasound extraction exhibited slightly higher phenolic and flavonoids content, as well as higher ABTS + radical scavenging capacity (4.63 mg GAE.g-1, 0.96 mg RUE.g-1 and 27.90 μmol TE.g -1 respectively). On both extracts, a high percentage of flavonoids was lost during simulated digestion, resulting on a bioacessibility of approximately 13 %. Extracts presented good stability during storage conditions, which indicates a possible technological application.

The lipolytic yeast Yarrowia lipolytica produces cell-wall-associated lipases, namely Lip7p and Lip8p, that could have interesting properties as catalyst either in free (released lipase fraction—RLF) or cell-associated (cell-bound lipase fraction—CBLF) forms. Herein, a mixture of waste soybean frying oil, yeast extract and bactopeptone was found to favor the enzyme production. Best parameters for lipase activation and release from the cell wall by means of acoustic wave treatment were defined as: 26 W/cm² for 1 min for CBLF and 52 W/cm² for 2 min for RLF. Optimal pH and temperature values for lipase activity together with storage conditions were similar for both the free enzyme and cell-associated one: pH 7.0; T = 37 °C; and > 70% residual activity for 60 days at 4, − 4 °C and for 15 days at 30 °C.

Despite goat milk having health benefits over cow milk, goat milk yogurt (GY) presents low consistency and viscosity, which reduces its overall acceptability by the consumer. Thus, new innovative methods can be an alternative to improve the quality of GY. Hence, this study aimed to investigate the effect of ultrasound (US) treatment with different sonication times on quality parameters of probiotic GY during refrigerated storage. US treatment was conducted at 20 KHz for 3, 6, and 9 min in yogurt. Lactobacillus bulgaricus and Lactobacillus acidophilus LA-5 were sensitive to US treatment, presenting a decrease in the yogurts stocked. This loss of viability led to reduced post-acidification due to smaller lactose metabolization in yogurt samples submitted to the US. Among tested treatments, the application of 6 min enhanced the apparent viscosity and consistency index of GY yogurts. In addition, this time also reduced tyramine and total biogenic amine (BAs) content. These findings suggest that 6 min of sonication is a promising way to improve the rheological properties and reduce the acidity and BAs content in GY. Further studies should be performed to optimize the US setting conditions to preserve the probiotic culture viability in yogurts.

Effect of sonication on the quality parameters of juçara, banana and strawberry smoothie was evaluated using a rotational central composite design with power (73.5–250.0 W) and time (7–36 min) as independent variables. The sonicated smoothie was evaluated regarding anthocyanins, instrumental color and rheological and physicochemical parameters. Within the evaluated processing conditions, 86% of anthocyanins were retained. The pH and acidity of the smoothie wasn’t affected by the independent variables. Regarding instrumental color parameters, only luminosity was affected by the operational conditions. The cavitation phenomenon decreased the apparent viscosity of the smoothie. The sonicated smoothie presented non-Newtonian behavior, with characteristics of a pseudoplastic fluid (n < 1) in all treatments and control. Taking into account that the highest anthocyanin retention was observed at 147 W for 2 min, this condition was the most recommended for the processing of the product.