Back to the kitchen: Food-grade agar is a low-cost alternative to bacteriological agar

Hydrogels as the plant culture substrates: A review

A class of hydrophilic polymers known as "hydrogels" have extensive water content and three-dimensional crosslinked networks. Since the old period, they have been utilized as plant culture substrates to get around the drawbacks of hydroponics and soil. Numerous hydrogels, particularly polysaccharides with exceptional stability, high clarity, and low cost can be employed as plant substrates. Although numerous novel and functionalized hydrogels might assist in overcoming the drawbacks of conventional media and giving them more functions, the existing hydrogel-based plant growth substrates rarely benefit from the developments of gels in the previous few decades. Prospects include the development of new conduction techniques, the creation of potential new hydrogels, and the functionalization of the hydrogel as plant culture substrates.

Culture media for clinical bacteriology in low- and middle-income countries: challenges, best practices for preparation and recommendations for improved access

BACKGROUND

Culture media are fundamental in clinical microbiology. In laboratories in low- and middle-income countries (LMICs), they are mostly prepared in-house, which is challenging.

OBJECTIVES

This narrative review describes challenges related to culture media in LMICs, compiles best practices for in-house media preparation, gives recommendations to improve access to quality-assured culture media products in LMICs and formulates outstanding questions for further research.

SOURCES

Scientific literature was searched using PubMed and predefined MeSH terms. In addition, grey literature was screened, including manufacturer's websites and manuals as well as microbiology textbooks.

CONTENT

Bacteriology laboratories in LMICs often face challenges at multiple levels: lack of clean water and uninterrupted power supply, high environmental temperatures and humidity, dust, inexperienced and poorly trained staff, and a variable supply of consumables (often of poor quality). To deal with this at a base level, one should be very careful in selecting culture media. It is recommended to look for products supported by the national reference laboratory that are being distributed by an in-country supplier. Correct storage is key, as is appropriate preparation and waste management. Centralized media acquisition has been advocated for LMICs, a role that can be taken up by the national reference laboratories, next to guidance and support of the local laboratories. In addition, there is an important role in tropicalization and customization of culture media formulations for private in vitro diagnostic manufacturers, who are often still unfamiliar with the LMIC market and the plethora of bacteriology products.

IMPLICATION

The present narrative review will assist clinical microbiology laboratories in LMICs to establish best practices for handling culture media by defining quality, regulatory and research paths.

Microencapsulation of Red Grape Juice by Freeze Drying and Application in Jelly Formulation

The aim of this work is to obtain new food products enriched with bioactive compounds from concentrated grape juice microencapsulated by freeze drying using a whey protein isolate-chitosan system. The obtained powder showed an encapsulation efficiency of (86.1±4.0) %, with an anthocyanin mass fraction (expressed as cyanidin-3-O-glucoside equivalent) of (1.4±0.2) mg/g, while the total polyphenolic (expressed as gallic acid equivalents) and flavonoid (expressed as catechin equivalents) mass fractions were (3.3±0.6) and (1.6±0.5) mg/g, respectively. The confocal laser microscopy revealed the presence of the flavonoid pigments wrapped inside the matrix, whereas the anthocyanins were grouped into large and compact clusters. The microencapsulated powder was used for jelly formulation. The new food formulations have a satisfactory anthocyanin mass fraction ranging from (0.03±0.01) to (0.12±0.02) mg/g, while no significant differences were observed in flavonoid content. All the value-added jelly showed appreciable antioxidant activity. The in vitro digestibility results confirm a slow release of anthocyanins from the food matrices during simulated gastric digestion and a significant release of the bioactive compounds into the gut. The addition of microencapsulated powder caused a significant decrease in firmness, cohesiveness and springiness, leading to the destabilization of the gel structure, while reducing the attraction forces between the matrix components. The sensorial analysis indicated that the panellists preferred the sample with grape juice the most.

Progress in the development of gelling agents for improved culturability of microorganisms

Gelling agents are required for formulating both solid and semisolid media, vital for the isolation of microorganisms. Gelatin was the first gelling agent to be discovered but it soon paved the way for agar, which has far superior material qualities. Source depletion, issues with polymerase-chain-reaction and inability to sustain extermophiles etc., necessitate the need of other gelling agents. Many new gelling agents, such as xantham gum, gellan gum, carrageenan, isubgol, and guar gum have been formulated, raising the hopes for the growth of previously unculturable microorganisms. We evaluate the progress in the development of gelling agents, with the hope that our synthesis would help accelerate research in the field.