Not yet. It may be tempting to start using the starter now, but for now, keep doing the daily routine of discarding and feeding. A functional starter is dominated by lactobacillus bacteria (which produce acid) and acid tolerant yeast. Before the bacteria start producing acid, other microbes are competing with the yeasts. These microbes,  often molds and unwanted bacteria, can often also produce carbon dioxide and cause your starter to bubble up. But they are tricking you. Told back from the temptation of baking with your starter just yet. From our previous work we know that very few starters reach their stable state before day 14, even fewer reach it before day 10.