Challenges and prospects of yeast-based microbial oil production within a biorefinery concept.

Biodiesel, unlike to its fossil-based homologue (diesel), is renewable. Its use contributes to greater sustainability in the energy sector, mainly by reducing greenhouse gas emissions. Current biodiesel production relies on plant- and animal-related feedstocks, resulting in high final costs to the prices of those raw materials. In addition, the production of those materials competes for arable land and has provoked a heated debate involving their use food vs. fuel. As an alternative, single-cell oils (SCOs) obtained from oleaginous microorganisms are attractive sources as a biofuel precursor due to their high lipid content, and composition similar to vegetable oils and animal fats. To make SCOs competitive from an economic point of view, the use of readily available low-cost substrates becomes essential. This work reviews the most recent advances in microbial oil production from non-synthetic sugar-rich media, particularly sugars from lignocellulosic wastes, highlighting the main challenges and prospects for deploying this technology fully in the framework of a Biorefinery concept.

Efficient use of discarded vegetal residues as cost-effective feedstocks for microbial oil production.

BACKGROUND: Horticultural intensive type systems dedicated in producing greenhouse vegetables are one of the primary industries generating organic waste. Towards the implementation of a zero-waste strategy, this work aims to use discarded vegetables (tomato, pepper and watermelon) as feedstock for producing microbial oil using the oleaginous yeast Cryptococcus curvatus. RESULTS: The soluble fraction, resulting after crushing and centrifuging these residues, showed C/N ratios of about 15, with a total carbohydrate content (mainly glucose, fructose and sucrose) ranging from 30 g/L to 65 g/L. Using these liquid fractions as substrate under a pulse-feeding strategy with a concentrated glucose solution resulted in an intracellular total lipid accumulation of about 30% (w/w) of the total dry cell weight (DCW). To increase this intracellular lipid content, the initial C/N content was increased from 15 to 30 and 50. Under these conditions, the process performance of the pulse-feeding strategy increased by 20-36%, resulting in a total intracellular lipid concentration of 35-40% DCW (w/w). CONCLUSION: These results demonstrate the potential of discarded vegetables as a substrate for producing bio-based products such as microbial oil when proper cultivation strategies are available.

Recent advances on physical technologies for the pretreatment of food waste and lignocellulosic residues.

The complete deployment of a bio-based economy is essential to meet the United Nations' Sustainable Development Goals from the 2030 Agenda. In this context, food waste and lignocellulosic residues are considered low-cost feedstocks for obtaining industrially attractive products through biological processes. The effective conversion of these raw materials is, however, still challenging, since they are recalcitrant to bioprocessing and must be first treated to alter their physicochemical properties and ease the accessibility to their structural components. Among the full pallet of pretreatments, physical methods are recognised to have a high potential to transform food waste and lignocellulosic residues. This review provides a critical discussion about the recent advances on milling, extrusion, ultrasound, and microwave pretreatments. Their mechanisms and modes of application are analysed and the main drawbacks and limitations for their use at an industrial scale are discussed.

Social media, body image, and the question of causation: Meta-analyses of experimental and longitudinal evidence.

This article presents four meta-analyses that can inform causality in the relationship between social media and body image; 24 experimental samples comparing the effect of appearance-ideal social media images to non-appearance-related conditions (n = 3816); 21 experimental samples examining the effect of contextual features (e.g., comments and captions) accompanying appearance-ideal social media images (n = 3482); 14 experimental samples investigating the effect of appearance-ideal images versus other appearance images on social media (n = 2641); and 10 longitudinal samples on social media use and body image (n = 5177). Social media appearance-ideal images had a moderate negative effect on body image (Hedges' g = -0.61, p < .01), were more damaging in higher- than lower-risk contexts (Hedges' g = -0.12, p < .01), and were moderately more impactful than other social media appearance images (Hedges' g = -0.68, p = .05). These effects were smaller but significant with outliers removed. Social media use had a very small, negative correlation with body image longitudinally (Fisher's Z = -0.08, p < .001). No significant moderators emerged. Clinicians should consider approaches to managing social media use, particularly exposure to appearance-ideal imagery, in case conceptualisation and psychoeducation for clients at risk of, or experiencing, body image disturbance.