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Acidic and chemical inhibitor stresses undermine efficient lactic acid bioproduction from lignocellulosic feedstock. Requisite coping treatments, such as detoxification and neutralizing agent supplementation, can be eliminated if a strong microbial host is employed in the process. Here, we exploited an originally robust yeast, Saccharomyces cerevisiae BTCC3, as a production platform for lactic acid. This wild-type strain exhibited a rapid cell growth in the presence of various chemical inhibitors compared to laboratory and industrial strains, namely BY4741 and Ethanol-red. Pathway engineering was performed on the strain by introducing an exogenous LDH gene after disrupting the PDC1 and PDC5 genes. Facilitated by this engineered strain, high cell density cultivation could generate lactic acid with productivity at 4.80 and 3.68 g L−1 h−1 under semi-neutralized and non-neutralized conditions, respectively. Those values were relatively higher compared to other studies. Cultivation using real lignocellulosic hydrolysate was conducted to assess the performance of this engineered strain. Non-neutralized fermentation using non-detoxified hydrolysate from sugarcane bagasse as a medium could produce lactic acid at 1.69 g L−1 h−1, which was competitive to the results from other reports that still included detoxification and neutralization steps in their experiments. This strategy could make the overall lactic acid bioproduction process simpler, greener, and more cost-efficient.

Cocoa is one of the food commodities that is favored by its high in polyphenols. The polyphenol and flavonoid in cocoa beans can prevent arteriosclerosis, diabetes, and their related risk factors. This research aimed to analyze the total polyphenolic contents (TPC) and flavonoid contents (TFC) of three cocoa bean varieties, namely LAM, TSH, and SUL1 collected from Lampung, Indonesia. The study also aimed to understand the effect of adding starter culture on TPC and TFC contents during cocoa beans fermentation. The TPC and TFC were extracted using ethanol from ground-dried beans and measured three times using a spectrophotometric method based on the Folin-Ciocalteu method at 760 nm and aluminum reagents at 510 nm. LAM variety contained the highest TPC and TFC among other samples at 62.8 mg GAE/g and 21.9 mg QE/g, respectively. The TPC and TFC decreased during both fermentation treatments with starter culture and non-starter culture. The TPC of cocoa bean with starter culture and non-starter culture decreased to 58% and 59% after fermentation. The TFC of cocoa beans with starter culture and with non-starter culture decreased after five days of fermentation, up to 58% and 75%, respectively. Remarkably, the TPC and TFC in fermented cocoa beans with starter culture were higher than those with non-starter culture. Therefore, it is concluded that three days of fermentation with starter culture can produce fermented cocoa beans with the preferred flavor/quality and maintain the TPC and TFC. However, the polyphenols and flavonoids content were reduced during the fermentation process.

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The chemical composition and sensory profile of cocoa beans are essential factors determining the quality of cocoa-based products. In this study, cocoa bean samples were collected from various regions of Indonesia, including Aceh, Banten, Bali, East Java, West Sumatra, West Sulawesi, East Kalimantan, and Yogyakarta. The cocoa beans were fermented and sun-dried according to the producers’ protocols and local practices. The sensory profile, fat content, total phenolic content, and the composition of sugars, organic acids, and amino acids of the cocoa bean samples were analyzed. The results revealed that the chemical composition and sensory profiles of the samples were diverse. The sensory profiles of cocoa liquor samples were described by low intensities of cocoa notes with the occurrence of fruity, floral, spicy, and sweet notes. The concentration of acetic acid, lactic acid, and some amino acids (glutamic acid, proline, and methionine) was associated with fresh fruit, browned fruit, and roasted note of the cocoa liquor, respectively. The variation in the environmental conditions and postharvest practices contributed to the diversity of cocoa beans’ chemical and sensory characteristics.